Hi,
What happens when you try to delete the video files, do you get any errors?
1. Click the Start button, click All Programs, and then click Windows Media Player.
2. If the Player is currently open and you’re in Now Playing mode, click the Switch to Library button in the upper-right corner of the Player.
3. In the Player Library, right-click the item that you want to delete, and then click Delete.
4. To select multiple adjacent items, press and hold the Shift key while selecting. To select non-adjacent items, press and hold the Ctrl key while selecting.
5. If prompted, click one of the following options:
· Delete from library only
This option deletes the link to the file from your Player Library but it doesn't delete the file from your computer.
· Delete from library and my computer
This option deletes both the link to the file from your Player Library and the file from your computer.
Note
If you previously selected the Don't show this message again check box at this prompt, and you want to change how the Player deletes files in the future, do the following:
· In the Player Library, click Organize, and then click Options.
· Click the Library tab, select or clear the Delete files from computer when deleted from library check box.
Remove items from theWindows Media Player Library
http://windows.microsoft.com/en-US/windows7/Remove-items-from-the-Windows-Media-Player-Library
Hope this information is helpful. Please let us know if you require further help.
Regards
Rehman – Microsoft Support