I help people out where I can.
A colleague of my gf had her PC pack up recently, she went out and bought a laptop but wanted me to fish her data off it. She dropped it off at our house with a couple of cd-rws and after a bit of messing around I was able to pickup the HD on my rig and copy the files over.
Turned out quite well in the end for me, probably only took me around an hour but she said I could keep her PC as she didn't need it anymore anyway. Not sure what's wrong with it (hopefully PSU and not motherboard) but even if I can't get it running again, the hd, memory and optical drives are worth a few quid.
I've spent quite a lot of time on the phone to my dad lately explaining various things about his PC, it's family, I'm not going to charge him for that when I think of all the advice he's given me down the years.
Generally speaking I regard it as just part of the 'favours network' anyway. I mean, say I help people out with the computers, then one of them is a plumber who can change a tap, someone else will drive places, etc.
Unless I literally slaved my guts out for a whole day on a computer I wouldn't expect any kind of payment. Most of the time I quite enjoy it anyway.