You'll need to take the disk out and connect it as a slave in another system (changing th jumpers to suit). Then boot into Safe Mode and take ownership of your folders and copy them before leaving Safe Mode.
Switch the mains off but kep it plugged in, earth yourself and open the case. Unplug the power connector and IDE connector, unscrew the disk and shove it another case by reversing the process. Move the jumper with some tweezers.