Ok, reinstalled Windows XP and it goes fine. The problem now is with YouTube. Videos are skipping but I don't think it's a problem with the graphic card drivers but with the low RAM.
I tried using Firefox and Chrome and a friend told me that it's because both software use loads and loads of RAM. Is there a way I can solve this problem? I can't install more RAM, that's for sure.
What else can I do? The laptop is being used by my 10-year-old son so he doesn't need that much, but videos are skipping especially if I put them on full screen. What can I do?