When you changed the mode, did you re-install windows?
I just set it to compatibility mode and installed Windows 7 32 bit, everything is working fine now.
When running AHCI on 64bit it ran fine, but when it was on AHCI, windows 7 32bit didn't detect it even though I had re-installed windows 7 with those settings. It beats me how an OS installs with a particular drive and then the drive just disappears afterward.