It'll get to the stage where it comes up windows xp home edition then turn itself off and then back on again.
I've tried starting it safe mode, back to last working order mode, safe mode with prompts, etc and it will just do the same thing each time.

I've just checked on HP's website and this model never came with a back up disc. It's on the pc already but I can't access it to amend anything on it.

Does that make sense?