That'll be Dell for you, my brothers' got a dell package and he wanted to put another HDD in, but the tower has been designed so that there isn't anywhere to put it!
There obviously a bit funny about their systems being altered with, I couldn't even partition his drive for Vista because of the hidden partitions that won't allow partitioning software to work. It seems the only way to do it is to completely wipe the drive first.
Regards
Martin