Firstly, reseat your hard drive, although I doubt this will fix your problem. I would suggest to try running the diags from the dell resource cd. If the hdd tests fail, then your hdd needs replacing. You could also try to install this hard drive into a desktop machine and copy the important data across. You could use a 2.5 to 3.5 adapter, or an external usb caddy to do this. Then try reloading windows on your existing hdd.