I have used PAT on a W7 64-bit system with two WD Black 750 GB drives and it somehow managed to get all the partitons aligned after many tries. I also used PAT on a Vista 64-bit system with two Seagate 500GB drives. It aligned all the partitions with no problems! I thought I had PAT all figured out! Now I'm trying to align another W7 64-bit sytem with two WD Black 640 GB drives and it won't align the boot partition no matter what I try. I have run chkdsk /F /V /R C: - no issues found. I have turned off protection and run several boot time defrags using Perfect Disk Professional 11 and run several "normal" defrags. I have shrunk the C: boot partition to 69.29 GB and have 55.7 GB of free space at the end of the C: boot partition. The Windows version of PAT does its thing and accomplishes nothing - Not Aligned is the result. The CD boot version jumps to the the screen that reads "If an alignment operation has been aborted or unexpectedly interupted...." It gives the following options: Undelete Partition, Boot Connector, Reboot Computer and Power Off. When I choose Undelete partition it selects the free space. I have run out of ideas on what I have to do to make PAT work on this machine. The only difference between this one and the W7 system it handled is a hibernation file. I have seen other people are having similar problems - any ideas on what I'm missing would be appreciated.