I don't say "I work in IT" anymore because you can almost hear little cogs turning as the person to whom you were just introduced is filing your contact details under "people to call if my PC's not working" and I can't be doing with it.
I now say, "I do network security and infrastructure development" which covers most of the stuff I do and doesn't have the same association.
I don't mind fixing PCs if there's an element of challenge to it (rootkit infection needs manual removal) or the local PC repair services are quoting obscene amounts of money to "fix" a PC by restoring it back to factory defaults when it shouldn't take more than a couple of hours to eliminate the problem in a way that leaves the data on the PC intact.
But I would never offer "mates rates" or "quid pro quo". I used to, though.
I gave away hundreds of hours of tech support to a couple who worked from home - they were friends of ours who'd helped us out by getting us in contact with a landlord when we needed to move at short notice.
A couple of years later, the landlord evicted us so they could move in. To add insult to injury they (not the landlord) spent our deposit money on decorating the property to their own tastes, and the landlord told us in effect to go to court if we wanted the money back.
Even after stitching us up in such a blatantly nasty way, they still had the nerve to phone me up and ask if I could help them!