Haha, thanks for the concern.
Luckily I've managed to get my PC up and running again, after many stressful hours.
But I've ordered a new HDD just in case, I'm not taking any chances. I am definitely looking for ways of cloning the contents of this hard drive on to a new one though.
Still trying to get Firefox and Spybot working again though, but I'm being extremely tentative, just in case my laptop dies again.