My mum's computer is showing weird characters at boot screen and even in BIOS instead of the usual letters. It cannot log into Win XP either, as the monitor switches off a bit after the Windows boot screen. Safe Mode works fine, with the weird characters still at the Windows boot selection screen, but not in Safe Mode. I've scanned for viruses and spyware but found nothing. She only uses it for word processing and music. I'm really lost here and don't know what to do else. Could someone please show me the light?

Try updating or reinstalling your video drivers first. Have you added a new video card? Sometimes you Bios has to be upgraded to support some of the video cards. Fool around with the BIOS as a last resort.

The video card drivers have nothing to do with the screens seen in the BIOS or POST screens. This sounds like some type of BIOS corruption. I would try clearing the CMOS.

Othehill is correct. The standard driver is used when in the bios. But it sounds more like a video card problem to me. Try reseating the card. Do yourself a favor BACKUP!