Well there are quite a few local directories. When I first started out with web design I put adverts in my local fish and chip shops. These have turned out to be some of the best repeat jobs I have had. What else do people have to do when they are waiting for their fish to fry but stare at the advertising boards. Another place to try is Church magazines, a lot of people dont have a clue about computers but have them to keep in touch with younger offspring.
Aside from that what did google adwords tell you were the best for you? I would try and get some links with the anchor text: "city/town pc repair". I cant imagine it being too competitive if it is try the next town down the road
Some local online directories may help just to get you on a page where people are actually looking. Free index appears to come up for the first term you listed.
Some ideas there for you to be getting on with. Word of mouth will no doubt be a big help in your line of work. I will try and think of some more ideas.
Matt