haha, your HD has the all the drivers from the other PC on it. So that means your windows is configured to the drivers of the old computer that your HDD was in. What you need to do is, back up your HDD which you should have already done. If not, you need to reformat because you wont be able to get into windows. The other option would be to connect that HDD to another HDD in working PC, then download a driver uninstaller. Then either download the drivers for the PC you want to get working, and manually put them into the HDD. I know, waiste of time, right? I think you should take whatever you need off of the HDD and then reformat and reinstall. If anyones got a better explanation, then listen to them. Im no expert but I have done what your talking about before. Is your HDD partitioned? Because then you could install windows on another partition and you would still have all your data except for programs that are configured to the original computer. Or you could try and run a repair. If you wanna do that.. go into your CMOS BIOS and change the boot order to CD-Drive first and then HDD. Put the windows disc in and then follow the directions for repair. Good Luck.