If this happens to you (or anyone else) again, I've found the go-to solution from my previous job as a repair technician. There are antivirus removal tools that

If this happens to you (or anyone else) again, I've found the go-to solution from my previous job as a repair technician. There are antivirus removal tools that basically do automatically what you did manually, purge the system of the antivirus files and registry keys. I've found them to work very well, even on later AV versions. For McAfee it's called the McAfee Removal Tool, and for any Symantec product, there is CleanWipe as well as the Norton Removal Tool. I am not sure of the legality of posting these tools publicly, but they are probably easy to find via search engine or torrent. May not help you if you're working with corporate machines, but I use them all the time for any machine I inherit or when helping out friends and family.