Screen Keeps Going Blank and Have to Turn Comp off with Vista

I bought this laptop new at Best Buy in Oct. and it had Vista. It waws fine
fro about the first week, but then I would be in the middle of ordering
something or looking at a site and the screen just goes white. I have to
turn comp off and back on and log in all over again. This is happening more
and more frequently. I have good virus protection and run scans frequently
to make sure I don't have a virus. I have heard that people had problems in
the past with Vista. Has anyone else experienced this and if so, what can I
do?
mgraw