I haven't read the entire thread yet, so forgive me if I repeat something that has already been said.
1. What services do you offer and how much do you charge?
I was thinking of the following
A. Computer speed optimization: $25
B. Custom computer building: $150
C. Data backup and reformat: $75
D. Computer networking and file sharing: $100
E. Upgrading the Operating System: $50
2. What other services do you suggest?
3. What about your business model would you change if you could?
1. I have not offered computer services. All I have done is help out friends and family, free of charge. A few people have suggested that I opened one, but I didn't want to commit. These are the prices I would charge:
A. $20
B. $50 (I would charge $25 for cable management)
C. $40
D. $75 (plus any hardware costs)
E. $20 (plus cost of OS)
2. Computer-cleaning. It is a very tedious job, but I think you'd be surprised how many people would pay if you explained all the cons that come with a dusty computer. I would charge $15 for a quick clean and $30 for a thorough clean (plus $25 if they wanted cable management). Computer repair. I would charge $20 (plus any hardware costs). I would also suggest overclocking if you're good with it. I don't know how successful this would be nor do I have a good price you could charge them.
3. N/A
**You can see that my prices are significantly lower than yours. Items A, C, and E require essentially hardwork. Item B is something we all enjoy doing. Plus, for an extra $150 they could just have Dell or HP build them one and they would have like 3-year warranties. Item D is really important and key. Yes, it is the most expensive of all because you'd have to include tech support. If something simple happens so that their internet is down, they'll blame you. If you have a tech support line, you can help them. You could advertise this service with free on-site tech support for a year. After a year you could just say free tech support by phone for the next 2 years. You'll have to get creative.
edit: So I have just read the entire thread. I have some additional comments to make. At first, I was under the impression that you wanted to do this as a full time job, in which case my prices may have been a bit low. The prices I listed will make you unbeatable when it comes to cost, especially if you do a good job. Word will spread, business will grow. Like said earlier (I'm sorry I can't credit this to the person, I forgot who said it), you can raise prices after you have high demand.
I would not recommend using Comodo. Comodo is very specific about which programs and processes they let you run and which you don't. When in doubt, there's always a pop up box asking the user permission for a program or process to access something. I would recommend AVG Free 9.0 + CCleaner. It will be simple enough for your average user to know how to work and it does the job. Just make sure to tell them to be weary of sketchy websites.
BUSINESS CARD! Giving people a business card allows them to use the information on that card, or the card itself, to give to friends. Word of mouth will probably be your best advertiser early on. Don't be hesitant to use social medias like Facebook and Twitter to get the word out.