Hey Skyper. I don't know really, what your problem is, but try following:
- plug the DVD-Rom and the HDD about one cable into the IDE or SATA port
- set the HDD to Master (by setting the jumper on your HDD) and the DVD-Rom to Slave (by setting the jumper in the middle section of the pins)

Now check in your Bios, if the devices can be detected to Master and Slave and try again. I had a similiar problem and it worked with this way. Check this thread out:
http://osx.kbot.de/comments.php?DiscussionID=19&page=2