Shaking a hacker

If you have signs your windows machine is being hacked, but virus checks
show nothing. Other than reinstall the OS after wiping your drive what
can you do to shake the hackers. Will reboot or change of mac address do
it? I don't believe any of these AV programs identify malware fully.
Microsoft itself I suspect is hacking their OS's. And probably most 
machines have hardware built in back doors. Or am I just wearing my tin hat 
again?