Can't Log into MY computer normally!

Hello,
I can not log into my computer normally, only in safe mode! I am running windows XP. When I get to the logon screen, I choose my account and enter the password, it starts to load up, I see the wallpaper, then a little box pops up with only a red X in it, and I can only click yes or no on it. If I do either, it logs me off & returns me to the logon screen. I can logon in safe mode, but not in safe mode with networking, or anything else. I scanned my computer with AVG in safe mode but it came up with nothing. Someone please help me!!