“windows media center cannot play this DVD please restart and insert the DVD again…”

This error message appears after you attach a USB drive with some DVDs and attempt to play them from Media Center.

To fix, open Windows Explorer, right-click ‘Computer’ and select ‘Manage’.

After the ‘Computer Management’ window opens, select ‘Disk Management’ under the ‘Storage Node’ on the left.

Right-click on the USB drive and select 'Change Drive Letter and Paths'.

Click 'Add’ in the dialog window, and when prompted, ‘Mount to the following empty NTFS folder:’.

Create a folder on one of the ‘permanent’, internal drives to use as a ‘shortcut’ for your mount. Now, whenever you attach the external USB drive to the computer, it should always automatically mount to the internal drive you selected. Vista should now see this as a 'permanent' drive and the error message should not appear.