[Beastie]

It's just that Windows automatically and inevitably becomes slower as soon as you install device drivers and the software you use everyday.
Plus the registry grows a lot with time (with no obvious reason) and it rapidly increases startup time from, say, 50sec to 1min 30sec on computers that are always cleaned of useless/temporary files, free of malware, constantly defragged and customized for performance (only required services are running, all useless features are disabled, swap space is fixed, etc.)
I generally don't have more than 30 installed program, and yet, within 6 months or so I can easily get a +50MB big registry, 2min long startup, programs that freeze on startup or closing (but work perfectly on FreeBSD), and most programs just start and run much slower.

This applies to every version I've used enough, that is, every version from 95 to Vista. I don't remember 3.x well enough.

Even better! On one machine I installed both W2K (probably the fastest and lightest modern Windows version) and FreeBSD at the same time just 2 months ago. I use Windows on it only once every week for a few hours. Windows still works fine but its startup time is already 1min 35sec, up from 55sec, while X is up and running within 50sec... as it was 2 months ago.

Lack of experience results in infected machines, badly installed software, and all. But I'm sorry, all the above has nothing to do with experience or computer-literacy, and there is NO way to fix it aside from un/re-installing software and ultimately the operating system itself.