Maybe a shot in the dark bur..Run a good registry cleaner and take out the ones you know(they are buggered already so..)A lot of programs when uninstalled from add/remove leaves something somewhere which you have to delete manually..

A fresh start altogether i think is worth it,unplug all the network pc,s as well start with the o/s then your antivirus sofware to prevent any intrution.Remember to activate firewalls and then all the other pc,s afterwards..

I know your valueble info is at risk bur we have all been there...We just keep forgetting to make backups regularly..

best of luck
vanman