How to disable scan at boot?
Could you please start regedit, go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager, select the value BootExecute and export it to a file? If you could post the file as an attachment here, I would like to check what could be wrong there.
In XP/Vista, if you press F8 when starting Windows and select 'Last known good configuration' from the boot menu, the boot scan should not be started.
You can find original locations of moved files in the boot-time scan report file (Avast4\DATA\report\aswBoot.txt), but there is no easy way to move them back automatically.
If you try to scheduling the Boot Time Scanning twice, you'll be able to unscheduling it.