Not sure what to charge for people in general when I do computer work for them.

Such as

installing a hardware firewall(smoothwall...ipcop...)

formating and installing an os

general virus/spyware issues

what do people in your area charge for various services or what do you think would be a good price for these?

I'd guess around 30 dollars an hour if your just a freelance fairly technical guy. If it sounds low; it's because in the end if your doing easy stuff it shouldn't take you that long and will allow you to get to another site.

The rate really depends on how good you are and what you are offering, professionals get around 50 - 60 an hour for onsite calls so you want to keep that in mind.