If you have the Operating System disk from the computer you are installing the HD into, try doing an operating system repair...I did this once with a hd drive from another laptop that I had...put the disk in the cd-rom and let it run and it should tell you "Operating system installed but it has problems" "Would you like to repair this Installation" or something like that...Click whatever it tells you to click to do the repair and then follow the prompts from there and you should be OK....