j2087,had a similar problem once. Solved it by putting in a "New" (not from another computer) HD and then did a format and partition --then installed an O/S and basically that got me up and running. I too wanted to use the Hd i had taken from another computer --so i installed it as a slave to the new one and it too was able to work.No one has asked if your "reused" hdd was properly jumpered and placed on the ide cable in the correct sequence. I assume it is the only hdd in your machine currently. So it should be jumpered to master and put at the 1st position on the ide cable. If you have access to another computer you can test the one that is currently not working in your present computer and set it to slave and connect it to the 2nd ide cable position and see what happens with it.good luck,truenorth