Thanks, it worked!
Just some information for others with this issue:
There was, however, one problem that is known to occur when enabling AHCI in the bios after
Vista has already been installed. Restarting the computer after the bios change will cause the following error:STOP 0x0000007B INACCESSABLE_BOOT_DEVICE
Fortunately, it's easily resolved by following the instructions here:http://support.microsoft.com/kb/922976
Something to do with certain drivers being disabled.