My Computer Dont POST, Not after a Walk Break

Just this afternoon after 2 hours my computer wont POST - Power On Self Test.

I has been up for about 8 hours from morning till afternoon, then I decided to go for a 2 hour break, then when I opened it just simply don't POST.

Being an IT, here is what I've done and checked:

1. Listen to any beep codes, its OK
2. Opened the casing and remove HDD power not to corrupt it from turning it on and off.
3. Removed RAM then powered it on hoping to hear any error beep code, no avail.
4. Re-connected my VGA cable to CPU box, no avail.

after these 4 procedures I decided to go for a walk thinking of what may just happened and the reports I need to pass today...

Guess my walk break works, I've re-connected the VGA cable at the back of my monitor and its power adaptor and everything is back to normal like nothing happened.

OK may be I just tired or something but I am happy that I can now write it up and send my reports :)

Was thinking that I may have something to do with my windows xp drivers but thanks it is updated and nothing to worry about it.