Hey guys! Recently my laptop started to run very slowly and then when I tried to reboot... it would load Windows and then freeze.

I tried to do a hard shut down and then it runs chkdsk, then freezes when it starts up again. Then I tried to start up on safe mode and same thing happens. I have McAfee running in the background all the time and still virus scan my computer every 2 days. The laptop is running Vista. Please help!!
Jen