Have you installed anything new that may have changed things. Consider absolutely anything you have installed as it could be that. If you can back up your laptop and then reboot XP that often for me cures 99% of the problems. However I am sure there are other things you can try before hand. Also a reboot tends to make things run a bit faster.
Thinking about it post typing have you gone on acer.co.uk and downloaded the latest drivers for your computer?