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Like hurricanes, viruses are often named after people. (Who could forget Melissa?) And just as a hurricane can devastate an entire community overnight, an e-mail virus can ravage the networked machines of the corporate world, system by system, leaving millions of dollars of damage--and heaps of aggravation--in its wake.

But of course viruses aren't the only grave threat to your computer. Bugs (see "The Swat Team: Kill Bugs Dead"), conflicting peripherals, unnecessary files, and--quite frankly--holes in Windows itself can cause headaches, downtime, and system slowdowns. To optimize your computer and protect it against these and other insidious agents, you need an effective tool kit of system utilities, including antivirus protection. Heavy-duty applications such as word processors and Web browsers may get most of the press and log the majority of downloads, but statistically, many more utilities fly off retail shelves.

Utilities are usually inexpensive, sometimes because their design or function is simple, in other cases because cutthroat competition keeps prices low. But despite their low price, are they good investments? Some of them, such as antivirus programs and system monitors, swallow up processing power and memory, slowing your PC. Others, like Registry diagnostics and system monitors, can be downright dangerous to your system if you use them incorrectly. Surrounded by stacks of utilities and several test PCs, we set to work to learn which packages deserve space on your machine.

For this roundup, we concentrated on the four most-essential categories of utilities: antivirus software, utility suites, diagnostics, and uninstallers/undoers. (For coverage of disaster recovery utilities, see January's "When Good Data Goes Bad." ) In each category, we scrutinized a cross section of products, including well-known titles from McAfee (a division of Network Associates) and Symantec, as well as Windows' built-in utilities and a few innovative packages from other vendors.

We tested a total of 23 utilities, including some updates that improve substantially on previous versions. After extensive comparisons of features, price, ease of use, and efficacy, we picked Best Buys in each category. Although some categories produced close races, Symantec's Norton products dominated the field, largely because of their stability, usefulness, and commendable customer support. But despite Norton's preeminence, utilities in general continue to evolve, and all PC users benefit from the competition.