Instant Reboot when trying to play videos

I was playing some videos on my computer (with Windows Media Player 11), one by one, and suddenly when I double clicked a video, I saw a flash of the blue screen of death, and it restarted.

My first thought was a virus, but I've had AVG (and Zone Alarm) up to date for months. I ran a full system scan and come up with nothing.

Now it seems every time I try to play a video, the BSOD flashes and my comp restarts!

Some recent things I had done before the crashes started include installing a new graphics card (GeForce 8800GTX), installing a new CPU (Athlon X2 4200+_ overclocking with nVidia's nTune utility (auto overclock), and running the CCleaner (crap cleaner) program.

I tried reverting the OC settings, but that didn't do it.
The crashes didn't start happening until a few days after OC'ing.

Any ideas?

Thanks in advance!

Windows XP Pro SP2
Asus A8N-SLI
Athlon X2 4200+
GeForce 8800GTX
2GB DDR400
X-Fi

 

I can't give you much advice on OC so I hope others join this thread.

I believe you may want to start by disabling auto restart so you can read the exact error.

Right-click My Computer>Properties<Advanced>Start up and Recovery>Settings>uncheck Auto Restart

 

I tried your restart trick, and I was able to see the error message, which led me to believe it was my video card drivers. I installed new drivers, and it works fine again! (I wonder how they got corrupted...)
Thank you!