Format the hard drive of your old computer.
Install fresh copy of windows. That will remove any viruses.
Access only your sensitive web sites only on the old computer. Such as banks, brokers etc.
Use the new computer for all other browsing without anti-virus. It will run faster! If it catches a virus, no big deal, you got nothing sensitive on it.
I’m not going to do that, that means I have to switch computers every other half hour.