CPUs don't get any slower as they get older, but it sure seems as if they do. The rapid pace of processor acceleration leaves power-hungry desktop owners with three choices. Buying a new PC every year is rarely practical. Suffering the ignominy of a behind-the-curve, slowpoke system, while friends boast about their blazing new machines, is no fun.

The third choice is to put a new engine under the old hood -- to upgrade your system's CPU. This option won't give you all the performance of a brand-new, bells-and-whistles PC, but it'll definitely give you a boost, and at a much lower cost than a whole new system. But CPU upgrades aren't for everyone -- and that doesn't just mean that they're possible only for desktop, not notebook, PCs.

"These [upgrades] are particularly for people who are interested in performance and are not afraid of getting their hands inside their computers," says Nate Dahl, a product designer at PowerLeap Products, which makes CPU upgrade kits. Many of these customers, explains Dahl, play 3D games and find their processors are hampering their frames per second even after installing a fast graphics card. Others are interested in upgrading to Windows XP, which requires more processing power than they have (Microsoft's official suggestion of 300MHz, most users agree, is at most half right).

Are You a Candidate?

Before choosing between the three ways to upgrade your processor, you must ask yourself if a CPU swap is really your best route to improved performance. First of all, are you satisfied with the other components in your PC, including not only the graphics card but hard disk, memory, and disk drives? Part of the value of getting a whole new system is the chance to get all the latest interfaces and devices, such as USB 2.0 and FireWire ports or a recordable DVD drive, built in.

If your hard disk is almost full, you'll want to add the cost of a new hard disk to that of a CPU upgrade -- which, with today's low PC prices, might tilt you toward the whole-new-PC option. The same goes for the amount of memory installed: Historically, adding more RAM has always been the fastest and cheapest way to improve performance, and if your desktop doesn't have at least 256MB, you're better off boosting memory to that level -- or, for Windows XP, likely 384MB or 512MB -- before adding more megahertz.

Finally, you need to have a realistic expectation of what a CPU upgrade can do. If you already have one of the last or fastest-of-its-type Pentium III or 423-pin Pentium 4 systems, you may already be at or near your system's ceiling. And, frankly, if you already have a 2GHz or faster chip, it's neither cost-effective nor commonsensical to chase after the last few ounces of power. Better to spend the cash on topnotch components.