Shell extensions which are blocked by default includes the Acronis shell extension, as it has a history of crashes and large memory leaks over the years.
The linked page has information on how to un-block it if you wish to. You may find it doesn't cause any problems, but make a mental note to try re-blocking it again should you run into problems in the future, as it could be the cause..
[Off-topic replies discussing various backup tools were split into a separate thread: Coffeeshop: Disk image backup software]