The computer I was using (HP Pavillion) does not show the POST, so I don't know if it showed the drive at that point. I went to Devices in Control Panel and the drive showed up there, as one of the two fixed drives. It also said that the drive was operating correctly, with no problems. But it did not show in My Computer, was not assigned a letter, and so I was unable to access it. It was a slave in the old computer, and the jumpers were set to that, I also put it on CS (cable select) but it did not recognise it there either, except for Device Manager. I know of no reason why the XP system would not recognise it. I also went to the Windows program selector (add new programs) and saw that the Plug and Play option had not been selected, but changing that did not let it read the drive either. Defies me...