Computer turns off randomly then no video signal on next startup

[d1d1]

Hand built this box in 2006 and never had problems. Just recently though the computer will randomly power off, and when I go to power back on the computer will turn on but there wont be any video signal. It'll take a few restarts for the monitor to start working again. Could it have something to do with the PSU or the video card? Pretty stumped.

 

[d1d1]

Also, just like to point out a few days ago I finally made the switch to Windows 7 from XP. Could the issue possibly be software side? Maybe some faulty drivers?