My Compaq A900 got to the point I could no longer restore the operating system, Windows Vista, possibly because a virus got into the partition. This PC will only take Windows Vista. I tried removing all partitions, but somehow the HDD became unusable for a fresh copy of Windows Vista to install from a DVD probably because of the way the HDD was set up by Compaq. I have been looking at setting up a USB boot stick with a program on it called HDDLowLevelFormat to re-initialize the hard drive so I can then install Windows Vista back on it. So far I've had no luck setting up the stick to do this. Can anyone help me with this particular task before I go nuts?