I don't know that much about computers so bare with me please.

I have a dell 5100 with windows xp and basicly i have a problem thats ******* me off. When i startup the comptuer loads as usual but i notice i get no pop ups on my desktop from my anti-virus software and thats how i know its happened. If i click my start button the start menu go's dead and i cant click in it, if i click an icon it just loads forever and nothing happens, then the only thing i can do is reset it at the plug.

Why is this happening? I mean i can sort it by restarting the computer a good few times but its anoying.

Thanks.

Suggest you boot up your computer with your XP Installation CD in the CD drive.
If your BIOS is setup correctly, will cause your computer to boot from the CD.
When it asks, you want select the Restore Point option.
Do NOT select the Install option.
The Restore Point option will basically rollback your system files.
Hopefully, it will be before whatever happened to your computer.
If so, then it might resolve your problem.

Please let us know the results of this procedure.

Good Luck...