Your computer won't reboot and you have tried several times. Windows won't boot properly? What exactly happens when it tries to boot up?
I would try using that computer's factory restore option if it has one. It might have a repair option. Also, you can try reseating that hard drive if it's a laptop.
You can try taking a hard drive out of that laptop and then reinserting to see if it will boot. It's most likely a faling hard drive then. You might be able to fix bad sectors on it long enough to get data off of it.
You would need a Windows XP CD or a hirens boot type CD to run a program that would fix bad sectors. Hard drives do fail. Usually there are warning signs and symptoms, but this is not always a case.
Have you tried putting that drive in a ziplock bag and freezing it for at least an hour? I've done it before and it works sometimes. It might allow Windows to run for around twenty minutes or so so that you can get data off of it.
It's not recommended to freeze your hard drive if you plan on taking it to a data recovery company as it can further damage that drive.