XPS420 with Vista will not boot; can't get to Windows System Restore

Hi,  I am very frustrated as this problem started happening within 12 hours of warranty expiration back in February.  Anyway, I will be working along and suddenly the computer freezes and I have to turn it off.  When I turn it back on I get the Dell window then another window which shows the copyright for Intel. It is then frozen again.

I have tried F8 at the Dell screen, but it will not come up. When this happened before several months ago, I was able to do a Windows System Restore and everything was fine, but now I appear to be in loop.  Is this problem due to having Vista? I do not get any system errors or blinking blue lights.  I am hoping this is easy to fix, but the manual is of no help since I can not get to the Repair your Computer screen to be able to run System Restore.

Many thanks for any suggestions.