Hi XKaLiBaR,

Welcome to the forum mate,

Sounds like your Mk4 drive is picky about what it will read, some are, try re-writing the backup on a different type of media (+r or -r depending on what you have.

It will be a bit hit and miss with backups, as the tolerance of the laser pickup will determine what the drive will or won't read.

If you still have problems then you can try;

Using a cd (this will work just as well as the dvd), like you have found out.
Using and OEM DVD.
Replace the laser pickup in the drive ( http://tinyurl.com/3psvc9 )

HTH

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.