As for speed:
XP is the best OS Microsoft have released (and probably will ever release, looking at their recent releases).
If I have two identical computers - one running XP and one running Windows 7 - the XP one will respond to everything faster than the Windows 7 one.
Windows 7 has fancy graphics that take up resources. I don't care for that and gladly sacrifice it for speed and improved stability (XP). Also there are some programs that don't work on Windows 7. But they work on XP.
The main reason I like XP is that you can play games on it, edit video, edit audio, use Bluetooth devices etc. And its all almost instant. You can probably do the same thing on Linux but I think it would take longer and be more complicated to set up.
Also, XP goes from POST to the login screen in ten seconds if you know what you're doing and disable a few services.
My point is just that it's a bit of a stretch
wink
to jump to Linux, spend hours installing it and configuring it when you could spend five minutes securing your Windows system.
Download
NoScript Addon for Firefox
Download
AVG Free or similar
Then you're done. Also programs and drivers for Windows are tested by Microsoft so I would assume they are more stable and work better than Linux programs.