.Windows becomes slow and choppy but it's just normal 'cause i install many games on it
and some autodesk and adobe apps that keeps processes running on background (punkbuster is the worst, i just play once in a week and have to keep it running all the time or the game(s) don't work anymore and i have to reinstall it to work again).Also, some latest game comes with anti-piracy daemons.
And i also think Windows folder system style so difficult to keep organized, there are lots of folders on different locations that stores application datas, man! They should make a /home/username, and give user the permission to write only this folder, so every configuration would be /home/username/.* , and every binary would lie within /usr/bin or sbin... like in "normal" systems, like Mac OS, Solaris, Linux... Also, windows command line sucks... even Mac OS has a better command line, and i never found someone who ever used it!
So, that's how i know. i reinstall windows once every year and scan it (using latest norton or kaspersky) to make sure there was no virus.
BTW; my Linux 32 install has 6 years, and i installed almost the entire Debian repository, and it is still stable and fast as if it were installed yesterday
.Windows XP sucks but i can't afford a newer one hehehe.