HELP – Vista will only boot in safe mode

Hello,
My pc crashed and after I have spent at least five hours scouring forums for a solution., i finally used the install disk to reformat and reinstall. It did it and saved the current settings as “windows old”
Everything went well, it rebooted while i had the disc in it after installing. I then removed the disk, and after it updated, rebooted to install windows updates.
Now it will only boot in safe mode again!
Can a virus get so far into the hard drive that it can prevent itself gettng wiped????
Anyway, im now downloading some malware programs, to see if i can find anything. The pc wouldnt load avg, so hopefully i can do get something to download.

PLEASE HELP!!!!!