Computer loads up xp screen then goes blank... but doesnt switch off

Hi, I have a new packard bell imedia 2770 and have not done anything new, (well appart from upgrade Norton Antivirus because my computer told me too for Vista) but it usually loads up. Now all i get is the usual packard bell load screen with all F2, F8 commands on, then the windows logo that loads, but after that the screen goes black, (but comuter is still running and when i clicked around on the screen, i must have gone on a user name becasue the loading up sound came on.

What is wrong with this because i cant seem to sort it out. Computer loads in Safe Mode and with Networking (hence im using internet to send this).
Please help because i have vital Uni work to do and i dont want to use safe mode all the time.

Thanks.
Daniel.