I use a crappy school computer (specs here) that gives max 30fps on Portal 2 and lags a bit on most newer Source Engine games such as Garry's Mod. I couldn't modify it because, of course, it's a school PC. I'm finishing school this year, though, so I need a PC, but I want something that I'll be able to upgrade and modify with a better GPU and CPU later when I have the money to. I'm too afraid to buy a refurbished PC from Best Buy or Walmart, because I had one of the Best Buy guys (and some others, too) tell me that if I bought an older cheaper PC, the motherboard probably wouldn't be compatible with say, an AMD FX or an Intel HD. I thought I'd come here for some advice on what to do. Thanks!