|Open help and support and search for event viewer.Should have link to it directly.|
Normally event viewer is under control panel, administrative tools, (but I am not in front of a Vista system right now)
Look for errors in red that are almost exactly the same time as your problem. They are kind of cryptic sometimes and you most likely will have to search for more help but gives us a clue.
If your system worked fine a few days or a few weeks ago you might consider a system restore point. Again start at help and support and search for restore.
Playing to the angels
Les Paul (1915-2009)