Vista contains the SATA drivers, you do not need to set the drive to IDE mode.
You should be able to set it to AHCI mode and be just fine.
Be sure you have the drive plugged into the correct controller, and that it is enabled. Some boards have more than 1, and some boards that have 5 or 6 SATA slots reserve some of them for RAID functions if you have it set up that way in the BIOS.
Read your manual carefully, I am sure that probably this is the case.
Try another plugin, and check your SATA settings in your BIOS again, there should be 2 places for the settings. 1 setting controlling 4 of the plugs, and another line controlling the other 2.
Non-the-less, standard IDE mode is only needed for XP install if you do not have the SATA drivers. Vista has the right drivers.