Reset Media player in Vista.

try this link http://support.microsoft.com/default.aspx/kb/925704/en-us

Steps to reset Mediaplayer in Vista.

1. Click Start - All Programs - Accessories
2. Right Click Command Prompt and select "Run as administrator"
3. Type the following command and press Enter.
regsvr32 wmp.dll
A Popup Regsvr32 will come up as the following: DLLRegisterServer in wmp.dll succeeded.
4. Launch the Windows Media Player. It should work fine.

Alternate Steps to reset the WMP in Vista.

Delete the following folder:
1. %USERPROFILE%\Local Settings\Application Data\Microsoft\Media Player
2. Locate and delete the following registry keys:
3. HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer
4. HKLM\Software\Microsoft\MediaPlayer
5. Restart the computer.