Vista Boot Up Problems

I hope someone can help me. I have a new Dell laptop and having trouble with my vista home premium operating system. After McAfee does a complete scan of my laptop, I have trouble booting up. When my laptop turns on, I get a blinking cursor and black screen. I can restart laptop if I do F8 and choose last known good configuration. But when I shut down my laptop and bring it up again later, I get the blinking cursor and black screen again. Dell has not been able to fix this problem. Anyone have any suggestions on how to fix this problem. Dell's solution is to go back to factory default settings every time.

I am using McAfee Total Protection 2007. Yes I believe when I do the complete scan, McAfee is deleting some files and that is why Vista is not booting up.