|Just a tip, in case you don't already know, when uninstalling an Anti-Virus make darned sure you stop it from running first. Same thing goes for third party firewalls. Reboot to make sure.|
Also some AV's leave a lot of junk around and most provide their own uninstall download to clear out the dregs.
Btw, hitherto Avast excluded scheduled scans from the free version (although they could be invoked by calling up ashQuick.exe via Windows Task Scheduler). Avast 6 free now has a "Wake up / Scheduled Scan" feature for running at night etc - if you like that sort of thing. Some folk do it seems: