For all of you that use Media Player Classic and have found out that it doesn't work properly (the screensaver is not disabled while playing) here is a solution:

Drop it! Anyway, Gabest that used to maintain MPC has also dropped the project and I would not expect a Vista compatible version. Instead this is the new kid in town

http://www.gomplayer.com/main.html

GOM Player is simply fantastic, it works like a charm and has all the features that MPC had plus many more. It is fast, with all the shortcut keys and zooming functions you would wish for.