[link|http://support.microsoft.com/default.aspx?scid=kb;en-us;278960|http://support.micro...d=kb;en-us;278960]

Windows Media Player 7.0 or Later
To disable the Windows Media Player 7.0 or later automatic update checks by editing the registry, use these steps:
1. Start the Registry Editor (Regedit.exe).
2. Locate the following key in the registry:
HKEY_LOCAL_MACHINE\\SOFTWARE\\Policies\\Microsoft
3. On the Edit menu, point to New, and then click Key.
4. TypeWindowsMediaPlayer, and then press ENTER.
5. With the WindowsMediaPlayer key selected, on the Edit menu, point to New, and then click DWORD Value.
6. Type DisableAutoUpdate, and then press ENTER.
7. On the Edit menu, click Modify.
8. Type 1, and then click OK.
9. Quit the Registry Editor.