first off, you cannot install windows on one machine then pop out the harddrive and plug it in another machine and expect it to work. you need to install windows on the machine you intend to use it on. but seeing as how you were able to install windows in another comp using the same harddrive, that kind of negates the harddrive as being the problem. when you first tried to install windows on your comp, did you hook the harddrive up correctly? also, the make/model of your harddrive would be nice.