Windows sludge: It's the invisible, undetectable detritus that collects on your hard drive and just mucks up the works. In the past, the clean install of a Windows upgrade could solve in one fell swoop all the little glitches that accumulate over time. But Longhorn's still a ways off, and service packs only go so far. I'll show you how to get Windows 98, Me, 2000, and XP back to their quick and reliable selves. And I'll describe how to toss an unfixable Windows setup and reinstall it from scratch.