office is good enough. Seems like you have everything planned out pretty well.
Just make sure that you have low prices and that you get the job done fast. That way your customers will definitely choose you to use your service again if they need their computer fixed.
Like bahawolf said, there are a lot of other companies too. So the only way you are going to make it is if you make sure that your customers are happy.
And being cheaper than the others are shouldn't be hard, my local computer shop charges something like 80e for reinstalling windows & drivers.
I was there buying some thermal paste for myself and overheard the discussion with another customer, almost told that other customer that I'll do it for 20e.