Windows 7: Random freezes...

Happend 2 times already today....

Just randomly freezes, once while browing web and once.. i dont know.. went for a cuppa and when i return.. its frozen...

then i have to restart computer from mains..

If i try to restart by holding the power button, the nothing comes up and the monitor just goes into sleep..

What is wrong?

Any help appreciated

Welcome,

Check for virus with anti virus scan, and download an run this: http://www.malwarebytes.org/mbam.php

If you come clean, I will give you the next step.