1. What is your hourly charge ?
 You would be surprised how many people fail to ask this.  It will help avoid sticker shock when the bill is due.
Typical Expected Answer  - $70 to $100.
Any higher then you are paying too much and  being ripped off or paying for this month's yellow page ad.  Any lower and it's someone doing it as a hobby and you're getting below par computer services.  You compare prices when you shop right?

2. Can you tell me how long or how many hours this is going to take ?
No one wants to get a bill for $500 to fix their pc, you could buy a new one for that price.
Typical Expected Answer -
Problems like this generally get resolve in x hours or less.
An experienced pc repair technician will have seen and worked on many problems, chances are they've done this type of computer repair before.  If not they most likely are not that experienced, Advice here, look for another computer repair service provider.

3.  Do you have or what is your minimum charge ?
Not all problems take hours to fix. Some may take only 15 to 30 minutes.  Either way it's nice to know how much this quick fix will cost out of pocket.
Typical Expected Answer -
Usually the minimum charge is 1/2 hour to 1 hour.  1 hour being the most common.

4. Are there any computer service charges besides the hourly rate ?
Some computer repair companies charge to pick up and drop off, some charge for estimates.  This is becoming more prevalent, so be aware of hidden charges.
Typical Expected Answer -
No. The computer repair service is costing enough already..

5 Do you charge more for Onsite Computer Service for In-Home / In-Business ?
Typically onsite service does cost more. This raise the per/hour rate $15 to $20. If they have to travel more than 15 miles there may even be an additional mileage charge.
Typical Expected Answer - Yes, on-site computer repair for  in-home / in-businesses generally incur a trip charge or slightly higher hourly rate. They may even charge for mileage if they have to travel more than 15 to 20 miles, if so you should look for a closer computer repair company, or ask if they provide remote computer repair