Hmm, does this happen when you open your D:/ drive but none of the others? And the D drive is where you store your films?
I'm going to take a wild guess that there's films or video clips stored on the root of the drive, and windows explorer tries to load preview "images" of them - this usually works fine, but sometimes (when there's an avi file larger than 2GB for example) it gets itself into a pickle and just gives up.
I might be wrong, but to see if I'm correct, go to start, run and type in these (separately, one at a time!)
regsvr32 /u shimgvw.dll
regsvr32 /u shmedia.dll
The above will disable explorer grabbing previews. Then reboot and see if you still get your problem. If you do and that's not the cause, then you can re-enable both with: