try a hijack this log... oh yeah, you tried A BUNCH of codecs and you dont think its a problem. Installing many different codec packs CAN cause problems a corrupt your current codecs.
I think you need to get your money back on those ESL classes...
Anyway, Nabla, if the video works fine in another machine, then that rules out a corrupt video (which is also possible).
Assuming your DirectX is up to date (it should be!) go to RUN and open the DirectX config utility (RUN: dxdiag).
Under the SOUND tab, reduce the hardware-sound acceleration level a step or two, close, then give things a try again. (You can also play around with the Display tab settings, too, but one at a time!)
See what that does.