After posting this, I noticed that whenever I restart my computer, sometimes it would work, and the next restart it wouldn't... very strange. It was getting really annoying as I wanted to install some of my games again. I've just looked inside, and the power cable was a bit loose. After switching back on, it seems to be working again, let's just hope it continues to work now. It was very coincidental that the power cable became loose when I formatted.
Thanks for you help.