So I have been working at a computer repair shop recently and fixing computers with lots of different problems. when we get a computer with a virus for service we throw in a free diagnostic in with it to make sure the computer it self is running fine. So let me take you through the process of how we fix most computers in the store.
The first thing that you will need is something called a hiren's bootcd which can be found this link
Once you have that burned to a cd or USB you then start the computer your fixing up and open the boot menu (normally Esc or F12) from there we go in the the windows xp mini. We mostly use software that is easy to use and that does not take someone extremely knowledgeable about computers to run. This is why we use windows instead of linux and command-line.
so next once the hiren's menu opens up we got to testing and then we use a program called S&M Stress Test to make sure that the computer's hard ware checks out. for instance does not have a bad stick of ram.
then from there after that passes we go and use Avira AntiVir Personal and SuperAntispyware and you need to make sure they are updated. then after that you will find a few problems most of them will be tracking cookies which aren't really viruses.
From there we restart the computer and then start it up in safe mode. And run the avira, superantispyware, and Malwarebytes. After all that checks out we restart the computer in normally and then run the last 3 virus scanners again.(malwarebytes is most effective in normal).
We then run CCleaner and Registry Mechanic to clean up the computer.
we then update windows using the windows update manager. We then check to make sure that the user has some form of anti virus protection if they do not we install avira for them or AVG
That is a simple way of fixing a lot of your virus problems.
hope this helps,
local tech repair admin