Help pls

Hello, sorry if this is the wrong section but I really need help.
My GFs has some hard disk problems. All of a sudden she couldn't boot up the windows anymore ( XP home edition; SP 1&2 ). As soon as that window picture apears the computer restarts. So I took her HDD to my place to try to save her data before formating the drive since she has some irreplaceble things on it and no back up. First I tried just pluging it in my PC but then not even my PC wouldn't boot, so I put it in an external hdd casing and access it over the USB but I stil couln't do it. When she bought the PC it had only 1 partiton so if I format it she will lose all.
When I plug her HDD in my computer he does apear in my computer as a component but I can't do anything with it. It allways has some error. When I tried looking at the properties of her drive it says; Free space 0, Used space 0, Format: RAW. So I guess that something is wrong with her HDD format.
So, does anyone know if there is a program that can format a disk without losing the data on it... or anyway to recover that date before formating it.
Pls help.
Srry for my bad english