Just sharing a problem I had with the excellent xboxhdm, since I noticed a couple of people moaning about it here and there, with no solution.
It seems, that for some combinations of south bridge and hard drive the kernels included on xboxhdm just won't mount that shiny new hard drive. (Xboxhdm just won't find the hard drive). I had this problem yesterday with two Maxtor DiamondMax Plus 9s, using my via based KV8 Pro - despite the utility working fine on my stock drive. It seems to be a problem the kernel used in the distro has with newer controllers that fork off a SATA line.
All the tricks I tried to pull didn't work - manual MS/SL setting, booting my linux partition from SATA and chrooting to the cdrom and fiddling with linux.
The only solution I found, was to borrow a machine made before the disc was put together. It's a motherboard issue and doesn't mean anything is bolloxed.