Trying a backup with the Windows 7's own backup solution to drive failed after a few seconds with an error message. After browsing various forums I have the note found that the plate with the "WD Quick Formatter" - must reformat program so that smaller (Windows7 - compatible) cluster are written. (Previously, still back up the existing on the disk WD Software ... Quick Formatter is actually not there, the program you have to download it from the WD website.)
The Windows backup has then works.