Faulty hard drive or corrupted operating system, or dead computer.
Try booting with some bootable CD/DVD. I recommend a Linux Live CD.
If you CAN'T boot with a bootable media, you have a serious hardware problem. This probably mean that you need to replace that computer. The data are probably OK. You'll need to install the drive in another computer to recover it's content, on mount it in some external casing and use it as an external drive.
If it work, then you know that there is a drive or operating system problem.
Try to access the content of the drive. If you can't, the drive is dead and need to be replaced. It's content is lost, or will cost a LOT to recover.
Install a new drive. Install the operating system, install all needed drivers (get them from the maker's web site) and your applications. A system factory restore is now IMPOSSIBLE.
If you can access the drive, back up your data to an external drive.
Reinstall or repair the operating system.
With Windows Vista or 7, sellect the "Upgrade" option. It will preserve your data and installed applications while replacing all OS files with fresh copies. Let Windows completely update itself.
With Windows XP, you can't repair like that and will need to reinstall everything, re-set any personalisation and restore your data.
Electro
March 2013
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