well I see that everyone is rushing to answer this one then :)
Oldboy, it could be so many different things,
Could be a problem with the camera drivers, download and install the latest ones, same with messenger, download and install latest version. Try it with nothing else plugged into USB (except keyboard and mouse if they are USB)
But...... 256mb of RAM is not enough for XP and may be the cause in itself.... increase that and it will make your computer sooooo much faster in general and may solve the problem. (bet your hard drive light is permanently flashing??)