Going to apply for a budgeting loan from the Social Fund. I should get around £300. Now, the problem with the computer is either the motherboard or the hard drive. If it's the hard drive, I can get a new one along with a non-OEM copy of Windows 7 (I'm wanting to do a major upgrade in the future, so will need this) for £175. Problem solved. If it's the motherboard, I'll need to get non-OEM Windows 7 anyway, as you can't change motherboards with OEM copies. If I want to keep my files (which I do, TYVM) I'll need a new hard drive too. So no money wasted. My CPU and memory, while not exactly high spec (2.33GHz Core2Duo and 2GB DDR2 respectively) are in good working order. So all I'd need is a Socket 775 motherboard, which will cost around £40 (oh, and some thermal paste, but that's like £2 or something). Well within budget.
...when did I get so good at thinking my way around problems? Why aren't I crying and having a panic attack? Go me!