Windows 7 locking issues

Can someone help me with an issue i have with windows 7 64 bit edition. Every now and again, my screen locks, well i thought it was my mouse freezing, but it turns out its not only that but everything, even my clock stops, so i loose time. If i press any key on the keyboard then the whole computer resumes as normal, its as if the computer is put into a paused state, i have disabled anything to do with power saving, and put in high performance mode for fault diagnosing purposes. This happens quite often, and i thought maybe it was something i had installed, but now i dont know, was previously running windows vista 64 bit without problems. can anyone help me identify the issue im having, its driving me mad.

everything is defo turned off, im clueless, the mouse pointer locks up when im using it, not after a time period. and it all comes back when i press a key on keyboard. haha, someone has to have an answer for this.