Hello @classicfan
Xperia Companion has a default path to save backup files, which is inside your "Documents" folder. Unfortunately, there is no setting to change this path.
The only solution I can think of is to change the default path of your "Documents" file from Windows itself by right-clicking on the folder -> Properties -> Location > assign a new folder on another drive. I use this method regardless to protect my documents in case of OS failure.
