Making my PC into a HTPC

So, I've got my low-end "gaming" PC and I'm looking to make it a bit more useful than just light gaming. I've looked into HTPCs and it sounds like a good route to take as we are moving house soon and Sky TV is mega expensive, so we're fed up of it. The idea of storing movies and shows on my PC ready to view any time just seems like a great idea. I'm just after some general information as to what modifications, if any, need to be made. Thanks again folks, this community is awesome.

My PC specs;

AMD A10 6800k APU

Gigabyte F2A88XM-DS2 mobo

8GB Kingston ValueRAM 1600 MHz

1TB Hard drive

Crap 500W PSU that came with the case

Windows 7 Home Premium 64bit

That would be fine for a home theater system.

I would suggest more hard drive space. Maybe a capture card or TV tuner, for television, and a media remote/IR card.