*cries* When it comes to girls, all logic seems to dissapear.
Don't feel bad. One of my neighbors (a 50+ year old male - sorry, no pics

had some computer issues. He was in the process of cancelling AOL and going over to NetZero. I assisted him a little bit initially. Then, for the next few days, he stopped by my house after he finished up work to see if I could do some more work on his computer. After about the 3rd day, I made it very clear to him that although I'm an IT professional, I can't keep working on his computer when I could be doing application/programming work for $50+ an hour. My comment completely offended him - I could tell by the look on his face. However, if I didn't cut the strings at that point, he'd still be hunting me down looking for me to do some work on his PC.
And, don't think that it's only girls where the logic disappears. I've worked with plenty of males where they suffer from the same issue. My neighbor was quite clueless when it came to PCs -- and really had no sense of logic either.
The unfortunate part is that once you touch the PC, you get associated with any issues or problems that develop. Even if something was out of place all along, the issue will get magnified by the owner of the PC once you've touched it. It's sad how people can take advantage of people like this. To handle these situations, I guess a "cut and dried" scenario might be the best method for handling situations such as this. The method could be undertaken as follows:
1) Present the person with the computer problem with a price quote up front.
2) They are now aware of what costs will be involved with fixing their computer issue.
3) If they agree to have you proceed with the work, you should:
3a) Have a backup drive handy.
3b) Back up their system with Ghost (or another similar software) to the backup hard drive.
3c) Work on their issue.
3d) If they start pointing out "oh, that looks different" or "that item used to be there" or ... you get the picture.
3e) When they start with that crap, you pull out the backup drive, restore their system to what was there before you started working on the computer.
3d) Once finished, you walk away. You might forfeit a bit of money, but you'll get yourself out of a situation that could cost you quite a bit more if you were to stick with it until the end. If the person is the type of individual as I described back up in "3d" - then, you are doomed. Because, they'll pull that crap while you're working on their computer and probably even weeks after you have completed the work.
It's really unfortunate that it comes down to the process that I've laid out. However, being a "nice guy" only means that you're the one to get burned in the end. There's plenty of people in this world who go about their daily lives taking advantage of innocent people. Don't fall into the trap of these individuals. If something doesn't seem right to you, then just walk away from it. If they're the type to take advantage of people, then they'll never sign your agreement that you present to them. Again, this is another "flag" for you. Follow the cue and walk away from the situation.