I just bought the 500 GB Seagate SATA HDD for my Dell Optiplex GX 620 system. I installed XP PRO in C: & Vista in the adjacent partition making it a dual boot system. I used it for a week with no problems. Then I installed a program called OSL 20000 Boot Manager.suggested by a friend to make it possible to install more than two OS. I also installed another program called Driver Magician also suggested by him although I had already installed the proper drivers but thought it might be useful in future. After installing those two programs I booted the computer 2-3 times & it seemed to work fine. But next morning when I started the system it will not detect the Hard Disk at all. If I connect the second Hard Disk, then that hard disk also doesn’t get detected. So this new hard disk makes all other working Hard Disks ( with XP on them ) also disappear. I tried normal checks like cable & power cord & drive does spin & tried to repaire thru Vista DVD but it says there is no hard drive. I need professional help because I have lots of data on it ( most I have backed up ) but returning for a replacement would leave all my data on it including personal data. Can you guys help ? Thank You.