Yes keep pressing the F8 key at boot up and select safe mode or you can try
safe mode with networking so you can try it on a internet website also.
My best guess is it is either a driver issue as justcallmebob said Windows update
might have updated one of your drivers and that is causing a conflict and that is
the reason why I never let Windows update change any of my drivers anymore
because it has happened to me before on my sound card and caused a conflict.
The other thing I can think of is it might be your IDE/SATA hdd cable going bad
I had about the same symptoms as you're having the system would freeze up on
the desktop or on a web site.
I changed the hdd SATA cable out and no more freezing up that is not until one of
my SATA burner cables went bad and it started doing it again changed it out and
the freeze ups were gone again.