I'm looking for a new computer for my aunt. Her hard drive died a few weeks ago, and her computer is so old that simply replacing it would be a waste of money. If she's going to replace one part, she might as well replace them all and just get a new computer. Her budget is ~$200-$300. She's against building her own, so I've been looking at pre-builts. I haven't come across one that I like within her price range, though.
She doesn't do anything intense. Just browses Facebook, gets her email, watches YouTube videos, and stuff like that. The only game she plays right now is SmallWorlds, which doesn't require a fantastic computer to play. The thing is though, that she wants to get into WoW. I don't see her doing dungeons or raids for awhile, so all she's really be doing is questing and running around when/if she plays.
So basically what she needs is a computer will be good enough for basic tasks and still get her decent (15-25) FPS out in the world on good/fair settings.
Like Fascinate said, that price range is going to be hard, and buying used PCs is not a very good idea. If she has a decent tower, powersupply, and DDR3 memory already then you could just do a MB, CPU and Video card upgrade.
This is an example and it would play wow on high settings if all she does is quest and 5 mans, raids would have to be done on good settings.