I've got a situation that has completely puzzled me, wondering if anyone can help. My friend asked me to fix her laptop, which has been failing to boot, getting as far as the blue Windows 7 login screen then hanging. The login UI doesn't load, it's just the blue background. I tried to re-install Windows from the boot disc, but when I put in the disc, I wasn't able to boot from it. Instead the computer booted from the hard-drive again and hung at the same place. This is after changing the boot priority in the BIOS. Since the laptop is out of warranty, and is to all intents and purposes a brick, I removed the Hard-drive, and connected it to my computer to see if I could reformat the drive from there. The thing that has really puzzled me though, is that my computer wouldn't boot when this hard drive was attached, despite running fine before I attached the drive, and after I removed it. Which leads me to think there's possibly a really malicious virus or something on the drive, which makes it the default boot device, despite having a corrupted operating system installed that won't boot. Has anyone heard of anything like this in the past, or have any ideas for a possible solution? The laptop is a Sony VAIO PCG-71312M, and the hard drive is a Toshiba MK5065GSX.