fix my PC

Awhile back my anti-virus software alerted me to the fact that my PC had become infected by a virus that copies keystrokes and screen prints and that can’t be removed by the anti-virus software. I stopped using my PC and started using my son’s PC (thank you).
I have looked up the steps on how to remove the virus and am confident I can do the first steps but the final step is to edit the registry and was not specific enough for me.

I need to either fix my PC or pay someone at Symantec or wherever to fix it. It’s ridiculous to have a nice PC and not be able to use it.