I don't mind doing computer work for friends, since computers are what I do, and I generally enjoy working with them, and I'm happy to help out a friend without expectation of monetary recompense.
I don't mind doing computer work for total strangers, because I don't know them, I don't feel much emotion for them, and it's easy to come up with a set cost structure in advance and enforce it. It's uniform, easy, and fair.
I hate working for acquaintances because I don't know them well enough to work on their computer at no charge (I've got too much stuff going on to waste my time like that), but I don't really wanna charge them the full price I charge for freelance consulting, either, since I do know them, if not well.
I feel like a jerk taking money from them for time spent, but I can't afford not to. I dread the question of how much it'll be, because I want to get paid for my time, but I don't want them to feel like I'm ripping them off.
And worst of all, I hate when things go sour on a job like that, because it's a pain to tell someone you know that it's going to take longer than expected, and cost more, etc.
Next time I get a request from an acquaintance, I really need to politely decline.