Just a warning to anyone with a recent Dell PC and SATA drives. Before you try to upgrade to or install Vista check your BIOS to see if it is set to RAID even though you do not have RAID. Change it to automatically detect RAID or ATA otherwise you'll get a BSOD with a "WORKER_THREAD_RETURNED_AT_BAD_IRQL error code 0x000000E1. I just wasted most of yesterday because of this.

And after some more investigation here's an alternate even better solution: Vista Installation solution for RAID setup/dual-boot that get worker_thread BSOD - Software - Vista - Dell Community Forum.