First off list your system specs

If you "just can't play video" and everything else is working narrow your problem down.

Is your system fast enough in its current state??

Reformatting will fix it for sure, but are these videos on your hd? Or you streaming from the net?

If its video, then its video. Try opening your box, and reseating your card make sure the fan is working keeping it cool.

The freezing could be from your video card getting too hot and locking up your pc. Video cards and freezing go hand in hand.

Make sure your players are up to date with the codecs and what not you need.

While your at it blow out your system of all the dust.

Save all your files on a separate partition or drive and start over is the best thing if you have all your progs, should take you about a day to get everything really nice and dialed.

And I don't utilize system restores, I maintain every setting manually. Plus Sys Restore takes alot of space..

drivers are important yes. get the latest and make sure you got your open gl or direct x stuff too. Calling on actions with non supported drivers can cause problems.