Getting mixed reactions here. Do I even go about trying to fix this or should I trying to run one of those programs that are being mentioned on it? And as I was wondering before, should I even bother trying to install an AV on it, or, should I go with what Slarty is saying and just reformat?

Generally to slave a HDD requires you to physically place the 'new' HDD into your PC and attach it via your own IDE cables, you might need to reset the pin link on the back to slave, and as this is a laptop, and I imagine you have a desktop, then you also require a bit of kit to allow the laptop HDD to fit your IDE .............
Loxley: Will this allow me to scan his pc with the AV I have on my laptop? Isn't there something along the lines of, if not one, a USB cable that would allow me to connect port to port and it would show up as and allow me to scan it as an external drive?

Haven't asked him if there is anything on his pc that he really needs, but am kinda leaning towards yes seeing how he is asking me if there is anything that I can do to begin with. He wants to take that pc at his house to his bar and hook it up to the bar's speakers and run the music through there.

what are the chances of you getting a second HDD, and cloning it ?
so when it happens again, you just swap and go cloning the ex HDD as a spare again ??
Will most definately suggest that to him... but if it does happen again, I won't even bother to try and give him a hand with it. I'll tell him to go figure out how to fix it for himself.