Q: I'm having video problems (such as green or pink lines on the video, choppy video, player hangs when playing video, and et cetera).
Q: Why am I getting video flickering?
A: Check for video card driver updates from your vendor, and/or DirectX updates from WindowsUpdate. If that doesn't work, turn down your hardware acceleration. Open WMP's View:Options menu dialog. You'll see a slider there for "Hardware acceleration". Turning this down to None often works around whatever driver bug is creating your issue (and sometimes turning it up helps too).
Some people have also pointed out that unchecking "Start player in Media Guide" in WMP's Tools:Options menu dialog gets a video issue resolved, oddly enough.
If NetMeeting Remote Desktop Sharing is turned on, that can also cause performance problems.
Note that on Windows .Net Server, video hardware acceleration is turned off by default (since it's not beneficial to server performance). Thus video performance will suck. If you want to be using a .Net Server box as a player box(?), you'd need to turn system wide video hardware acceleration up. You can do this via right clicking on the desktop, choose Properties:Settings:Advanced:Troubleshooting and move the acceleration slider all the way to the right. You will also want to turn on DirectDraw - go to the Windows Start button, then at the Run prompt, enter 'Dxdiag'. Click on Display. Click on Enable DirectDraw if present.

HTH