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Memory

Computer memory may not get worse with age, but it does get outmoded. Older DDR SDRAM is rapidly being supplanted by DDR2 memory, which in turn will be overtaken by faster DDR3 memory when it becomes available within the next couple of years. As with processors, each type of memory requires a motherboard with a compatible RAM socket, meaning that you can't just pop DDR2 memory into a computer designed for DDR SDRAM memory. But regardless of what type of RAM your system uses, adding more remains one of the cheapest and most effective upgrades.

Faster memory is desirable, but the most important thing is having enough. PCs slow down drastically when they run out of real memory and have to start swapping data into much slower virtual memory on your hard drive. That situation often arises when you run many applications at once, or when you use video-editing or other programs that shuffle a lot of data. Our tests, which involve working with images and using Nero Express to burn CDs, ran one-third faster when we upgraded from 512MB of RAM to 1GB.

Generally, 1GB of memory is enough for Windows XP. But if you want to use Vista with your existing system, you may need more memory. Because of new features like SuperFetch and larger overall memory demands, most analysts agree, Redmond's new OS will be happiest when working with 2GB or more.

For a quick, informal check of your memory needs, open a typical set of applications. Then open the Task Manager and click the Performance tab. Look at the line for 'Available' under 'Physical Memory (K).' If things feel sluggish and the reading is near zero, you need to shop for more RAM.

Before you buy, use a tool such as Sandra Lite (see "Gauge How Hard Your System Is Working") to figure out the type and amount of memory your computer currently has. Or head to a site such as Crucial.com or Kingston.com, enter your motherboard or PC model number, and receive an automatic ID of the type of RAM your system takes. Most PCs being upgraded today use dual-channel memory, which must be installed in pairs for maximum performance; so be sure to buy two matched chips when arranging for your upgrade. Typically, you'll have to install the RAM in alternating slots--1 and 3, or 2 and 4--to use dual-channel memory access.

Since most motherboards have a maximum of four sockets for memory, you may have to pull out some (or all) of your existing memory before adding new modules. Also, check your current memory's speed with Sandra or another diagnostic program. Though many faster chips may be compatible with your system, they will all operate at the slower speed if you use a mix of slower and faster memory modules.