|As best I understand, the "free" version is just that - free. Possibly one may have to reregister at some future date; but again it will remain "free".|
Avast free version requires one to reregister at intervals; but remains free nonetheless.
Other free utilities to consider:
Adwcleaner - http://www.bleepingcomputer.com/dow...
Junkware removal tool - http://www.bleepingcomputer.com/dow...
Both very safe to use; free; and the downloadlinks are safe etc. Regularly recommended here.
Nonetheless when you install " any" utility, including the above, opt for custom install not automatic; as that way you can deselect "anything" that might otherwise be installed by default ("automatically") apart from actual/specific utility itself.