CNET's desktop buying guide

The brains of any PC is the CPU, or central processing unit. It is the single most important component, but that doesn't mean you need to rush out and splurge on the processor with the fastest clock speed. Both Intel and AMD charge a premium for their top-of-the-line CPUs. For most users, we recommend scaling back a notch or two. You'll save a lot of money, and generally speaking, you get better bang for the buck with more memory.

PROCESSOR	DESKTOP TYPE	PROS AND CONS
Intel Core 2 Extreme QX6700	Performance	If you turn your nose at dual-core processers and have cash to burn, take a look at this chip with four distinct cores. Though there are no major vendors offering this expensive chip in their desktops yet, you can check out some white boxes from smaller hardware retailers.
Intel Core 2 Duo	Performance	The first dual-core desktop chip, this processor stole the performance crown from its long-time rival, AMD. There are four different speeds available at different price ranges.
Intel Pentium D	Mainstream	The majority of today's PCs use a Pentium D. A good all-around chip with hyper-threading capabilities, it has been overshadowed by the Core 2 Duo processor.
Intel Celeron	Budget	Inexpensive, but a bit slower than Intel Pentium chips.
AMD Athlon 64 FX	Performance	Instead of putting four processing cores on a single chip, the Athlon 64 FX platform allows the uses of two Athlon 64 X2 dual-core hardware in a single system. This setup allows for a larger memory bandwidth for data-intensive tasks.
AMD Athlon 64 X2	Performance	The first dual-core offering from AMD, the Athlon 64 X2 has 64-bit support as well as distinct memory caches for each core.
AMD Athlon 64	Mainstream	The first 64-bit CPU for Windows desktops, the Athlon 64 has native support for today's 32-bit applications and operating systems, and it delivers blistering performance that will only improve when Microsoft releases a 64-bit version of Windows and software developers begin to roll out 64-bit apps.
AMD Sempron	Budget	A good bargain, but has long been fading from the market.

The speed and the amount of memory you choose go a long way toward dictating your system's level of overall performance. For a machine running Windows Home Vista Basic Edition, 512MB is the bare minimum. Double it to 1GB, and you'll see a big difference, especially when running multiple apps concurrently or using intensive image- or video-editing applications in Windows Vista Home Premium Edition and above.

The speed of the memory is also critical. Make sure the memory is DDR2 (double data rate) SDRAM. Midrange PCs can get by with 533MHz memory, though faster 667MHz memory won't set you back too much more. Written in one of two ways, memory speed is referred to by the speed in which it communicates with the CPU (1.8GHz, for example) or by its data bandwidth (5.3GB per second or PC5300). Though faster memory is available, today's chipsets do not support anything faster than 667MHz (without overclocking).