weird it works in 7.0 and not with 7.1. even tho the P5-90 is relatively old (siz years I think?).
your CDR is non-ATAPI, I think with a recompile of the kernel u can add it, but Im not sure about that.
the Gateway 2000 P5-90 motherboard possibly has buggy RZ-1000 and/or CMD640 EIDE chips. I know with a kernel recompile can add support for it.
Ive looked around, but found no other clues than adding "hda=serialize" at the bootprompt.
It isnt the most pretty option but if no one has a definitive answer I would suggest installing 7.0 again and upgrade over that.