Ok so let's get this straight before I or anyone else attempts to provide you with a possible solution. You have a single wireless router, and you are trying to set up a wireless network, and share a...

You can also download the K-lite codec Pack for free... that should help with alot of problems. It might even solve your thumbnail problem for the MPEG.

Yea reinstall WMP, QT, Divx (If you have allready), and any other media player on your system.