Hmm...
Boot into safe mode (can usually be done by typing and F key, or delete or ESC.
Go to Start> Run. Type msconfig Go over to startup, and uncheck any boxes you don't need to start up (such as RealPlayer, AOL, etc etc) But be careful, you may have to google a few of them to find out if you can disable them from starting up or not. Then, go to Start> Programs, Startup. delete all of the entries.
This should help, and if it booted successfully, if you want, you can enable services one by one until it happens again, then disable that program from loading on boot again.
Hope this helps!