When is it worth upgrading your old warhorse, and when should you trade it in for a spiffy new thoroughbred? Here are some tips for deciding when it's worth upgrading and when it isn't.

Your Use of Your PC. What applications do you use on your PC? Do you run resource-gobbling CAD apps, state-of-the-art games, or advanced graphics programs such as Adobe Photoshop? If you're running such programs on older PCs, you're wasting too much time staring at an hourglass cursor. Upgrade, or buy a new machine. Spend most of your time working the keys on a word processor or casual Netsurfing? You don't need a cutting-edge machine; your older machine will probably do fine for you, perhaps with an upgrade or two. Usually software manufacturers provide "Required" and "Recommended" hardware specifications for their products; you can bet that most "Required"" specs do little more than get the program up and limping. Your machine should meet or exceed the "Recommended" specs for that program to really giddyup. But use some common sense, too. If your machine does what you want it to do, then why upgrade? Computer geeks and computing magazines keep yelling, "More! More! More!" and "Faster! Faster! Faster!" at us, but if you don't need to do more or to go faster, save your money and do something else with it.

Memory. We've talked about memory before, but it's worth repeating: a memory upgrade provides the most bang for the buck. We're talking as little as $1-$4 per MB here. (Remember, your PC loads running programs in RAM; if it runs out, it's forced to "swap" back and forth between loading and reloading different portions of the program, and that's a timewaster.) An old 486 needs at least 16MB of RAM, and a jump to 32MB will really get Windows up and running. Lots of us are still running plain vanilla Pentiums (Pentium Classics, some shills are calling them) with 16MB under the hood; zapping them to 32MB, 48MB, or 64MB definitely puts a tiger in their tanks. Machines with Pentium IIs and/or Pentium MMXs often come equipped with 32MB of RAM -- think about upping these to 64MB or even 128MB. Added memory speeds applications and makes it much, much easier on your machine to run multiple apps, particularly memory hogs like PowerPoint, Office 97, or Lotus Notes. Here's the tricky part: all memory isn't alike. Old 486s and Pentiums usually run a flavor of RAM called EDO. Most P-IIs run SDRAM-66, and newer, faster Pentium III/IV and AMD Athlon systems prefer the hi-test version called SDRAM-100. If you aren't sure (and why would you be?), ask the guru. Besides, even though this is considered an "easy" upgrade, you're probably smart to get someone to install the new memory modules for you anyway, so run it by him or her before you buy. Just remember that some systems need "parity" memory while others prefer "non-parity," and that SIMM and DIMM flavors of memory don't co-exist well, even if your computer has sockets for both (some P-MMX models have EDO DRAM memory but include open DIMM sockets for later upgrading).

Need to know exactly what kind of RAM your system needs? Visit www.kingston.com/ and click on "Find the Memory You Need." You can search by manufacturer, part number, or generic memory. Kingston provides memory for desktops, notebooks, servers, workstations, routers, and printers as well as flash memory.

CPU Upgrades. With sleek new speed demon PCs available for way less than $1000, upgrading your CPU and/or your motherboard is much less of a cost-effective upgrade than it used to be. A few guidelines: If you own a Pentium 66 or older PC, don't bother with a chip upgrade, buy a new 'puter. One magazine says if you own anything slower than a P-200, buy a new one, but I don't know about that. If you own a P-75, P-90, P-100, and your BIOS can be upgraded either by software or by purchase of a new BIOS chip, AND your PC uses a Socket 5 CPU module, you might consider buying a packaged CPU upgrade kit such as Evergreen's Mx-Pro 233 (www.evertech.com/) that includes upgrade goodies such as a cooling fan, a heat sink, software for dealing with BIOS upgrades, and (most importantly) a voltage converter. (Systems with one of these chips but without a Socket 5 CPU module can also use Intel's 200-MHz Pentium Overdrive Processor with MMX Technology Kit from www.intel.com/). If you own a Pentium Pro, consider Intel's Pentium II Overdrive Processor with MMX Technology Kit. Unfortunately, this upgrade costs $550 -- probably not worth it. (Still, if I were giving the advice, I'd say buy a new machine. Why spend money to upgrade to a slightly less obsolete system?) If you have a Pentium faster than 100MHz, or a Pentium II, you can find an upgrade for relatively cheap, and double your clock speed in the process. (One machine I read about, an old PII 350-MHz dinosaur, showed a 57% improvement in performance after the owner installed an Evergreen 1.1 GHz Performa III upgrade kit, for $170 and a weekend's labor.) Don't plan on plugging a P-II, III, or IV chip into your old Pentium PC -- the chip sizes aren't the same (clever devils at Intel, huh?), and don't buy an ATX motherboard unless you're already planning to buy a new case to accompany it. (PowerLeap at www.powerleap.com/ is another good source of CPU upgrade kits.) Good news on the CPU upgrade front: Evergreen is marketing CPU upgrades on a PCI card, which means that any computer that can accept PCI cards (including some 486 systems) will be upgradable to P-II performance levels. It should cost you around $350 to $500 to upgrade your critter to a Celeron II CPU with 64MB of RAM. But if you really want to hot things up, you need a motherboard transplant, and that ain't even cheap; with sub-$500 PCs out there that are perfectly acceptable machines, why bother? And by the way, do I need to warn you to leave CPU installations to those who are certified to do it?

Want to upgrade to an XP-compatible system from a PII or old Celeron? Evergreen sells a 1 GHz Celeron-based upgrade kit that works nicely. Of course, with the kit costing $260 plus the time and labor of installing it, and with new PCs selling for as low as $500, you might not want to think about this. If you don't want to transfer a lot of files and programs from your old PC, though, it's a choice worth considering.

If you're thinking of this type of PC upgrade, take some precautions before getting out the screwdrivers and the bourbon. First, image your drive. CD-RW disks are the easiest and cheapest way to do this little chore. If you don't see the need, then at least copy crucial data files onto disk before moving ahead. Next, XP users should call 1-888-571-2048 with their Product Key number to avoid XP's balky Product Activation hassle. All users should back up their BIOS settings. Double-check your expansion boards and cables to see that everything is seated and connected properly. And lastly, don't wear polyester when you do this (or anything involving playing with the hardware). Polyester conducts static electricity, and static electricity can fry your system in a microsecond. This means you, Leisure Suit Larry.

Hard Drives. A good choice for a relatively cheap upgrade, and not a bad way to test whether or not you can actually perform surgery on your PC. If you're running a 486 or old Pentium (slower than, say, 90 MHz), then don't bother -- instead, tuck your money away for a new machine and save hard drive space by archiving files or deleting apps. If you're running an older machine, think about an UltraDMA drive with an UltraDMA controller, and be prepared to upgrade your BIOS. Running a PC less than a year old? Shoot for a 6GB EIDE drive. (A smaller drive is pointless, unless you're really, really pinching pennies; $50 extra can buy you 2 or 3 more gigs of hard drive space -- not a bad bargain.) If you really want to get into storage, you can go all the way to a 17GB hard drive or higher. It won't be cheap ($250+), but you'll have hellacious drive space. If you run a PC that acts as a network server, or runs heavy data- or graphics-intensive apps, you might prefer a SCSI hard drive. A SCSI drive is more expensive but operates such apps much better than the industry-standard EIDE drives. Hard drives aren't that difficult to install, but definitely not an installation for the novice. If you've been doing little hardware tweaks such as installing more RAM without running into difficulty, then you might be up to the challenge of installing a new hard drive. Otherwise, let the wonks do it. Tip: since newer hard disks are faster than the dinosaur on your machine, install the new one as your main C: drive and transfer everything over. Use the older hard disk for supplemental storage or data backup.

High-Capacity Floppy Disk Storage. Adding secondary or new, larger hard drives is one option. Another is to install an Iomega Zip, Jazz, or Clik! drive, a Castlewood Orb drive. or a Superdisk LS-120. You'll enhance your storage capabilities a good bit, and you'll do it on the cheap (the basic Zip or Superdisk drives start around $80, and an Orb 2.2GB cartridge can be had for $30).

New CD or DVD Drives. Don't even consider upgrading your 4X CD-ROM to a speedy new 32X or 40X drive, unless you routinely access programs from your CD drive. Why? Almost all software titles are written for 2X or 4X drives, so your faster drive won't get much chance to flex its muscles. The only reasons to install a fast new CD-ROM drive are either because your old one is dead and you don't want a DVD or CD-RW drive, or you run programs from CDs frequently, in which case you'll probably want to wring every drop of speed you can from your CD drive. DVD-ROM drives are the wave of the future; if you're of a mind to upgrade, think about replacing your CD drive with a DVD drive instead. They come in two flavors, DVD-ROM, which plays both CDs and DVDs, and DVD-RAM, which only plays DVD-RAM cartridges and are primarily used for heavy-duty storage. CD-RW drives are most useful for those who do a lot of work with music, graphics, or video files on their PCs. (Forget the old fogey CD-R drives. The CD-RW drives have superseded them, and cost no more.) (Note: Budget watchers, the onset of DVD drives has driven the price of standard IDE CD drives way, way down.) Of course, if you're running a machine slower than a P-II 350, a DVD is out of the question. Even a CD-RW may balk on an older machine. And unless you really, really know what you're doing, don't even think of installing a DVD-ROM drive. CD-RW and DVD-RAM installations are no picnic, either.

Graphics/Video Cards. A good idea, right? Slap in a snazzy new video card and watch those Klingon battle cruisers snap to. Well, maybe not. Those of us who do primarily word processing or other work that doesn't depend on heavy graphics reproduction probably won't benefit much from a new video card, unless you're into games. Gamers love graphics, the faster and more realistic the better. In that case, either upgrade or save for a new machine. If you run graphics-heavy apps such as digital photo reproducers, you should have at least 2MB of video memory -- 4MB would be better. (Warning: the new office apps such as Office 2000 are a lot more graphics-intensive than their predecessors, so a good graphics card is a must for these programs.) An 8MB video card is only useful for CAD or graphics pros who use 21-inch or larger monitors. It is possible (and labor-intensive) to just upgrade the video RAM on your current card, but it's a lot easier to just stick a new video card in there. Remember, all the video memory in the world won't make Quake or AutoCAD look good on a 15-inch monitor, and if you don't have a good grounding in working in a PC's innards, you probably want to have a pro do this install for you. The good news? A top-flight video card compatible with all but the very old machines can be had for under $100.

Find out what kind of graphics card you have by right-clicking My Computer, selecting Properties, clicking the Device Manager tab, and double-clicking Display Adapters. The card and vendor will be listed. To check the driver, double-click on the card name and click the Driver tab. In Win 98, open the Components section of the System Information utility (Start/Programs/Accessories/System Tools/System Information).

Sound Cards. Many older systems don't even have stand-alone sound cards, since their motherboards have integrated sound chips. 3D sound, particularly Microsoft's DirectSound3D, changed that. Now a sound card is essential if you want good 3D surround sound. Forget about ISA cards, PCI is the wave of the future, and much, much easier to set up than ISA-based cards. Make sure your PC's chassis has enough room for the new sound cards. And choose a card that offloads processor-intensive tasks to a sound-processing chip, otherwise you'll experience significant system slowdowns.

Modems. Agh. If you're running a 14.4kbps or slower modem, read no further: upgrade that sucker right now. Now. Go. If you're running a 28.8 or 33.6 modem, you definitely want to think about going to a V.92 modem (the new 56kbps modems combining the old, competing x2 and K56flex technologies). If you already own an x2 or K56 modem, you might be able to get a free upgrade from your vendor (no promises about ease of upgrade, though), but as the price of V.92 modems continues to drop, look for these upgrade offers to fade away. However, if your ISP doesn't yet support V.92, wait until they've switched over before you switch, even if it means plodding along under the older standard for a while longer (visit modemsite.com/56k/v92isp.asp to find a compatible ISP in your area). External modems are no harder to swap out than swapping a printer, but changing an internal modem is tricky. Thinking about going to cable, ISDN, ADSL, or other cutting-edge technologies? Check here, and with your phone company and your ISP before making the switch.