Retail. I know very little about PC hardware, but I like doing things myself, so they give me parts that work and I put them together. Since the last almost 3 years now I've taken my business to the same shop, and I'm getting quite a few advantages from that. They'll give me the occassional free thing (like adapters, or USB sticks), and fast repairing when I mess things up.
I realize I could find the infomation online aswell, but that doesn't have any assurance it'll work. If something doesn't work like they say, I just go back there and have it switched to something that does.