I think your service is needed. My question to you is why are they getting in touch with you rater than Geek Squad or just taking their computer in to Best Buy? Is it because you're charging them less (or nothing) or because they've heard great things about your work? If you're doing this work for free, this may be why the work is finding you... if you start charging, then it may not find you anymore....

I think you can certainly monitize what you're doing - e.g., $50 per hour for a house call or $25 per hour for remote help. I guess you would need to determine how long it takes you to fix stuff to know how much to charge. You should also probably get a price list of services from Geek Squad - that may give you a better idea of what to charge.