I formatted the SD card using Windows Vista and SD Formatter. Then I copied NOOBs files, inserted it into the PI3 and installed all my softare (Raspberry...). The system works but I am unable to backup the SD card on my Windows PC using either Win32DiskImageer or Roadkill. Even Windows File explorer cant open the SD drive and from all software I get asked if I want to format the drive.
When I first installed my PI3 using Win32DiskImager and Raspberry I could back up from time to time but in the end I tried it again and had the same problem as now. That was with a 16 GB card.
What could possibly cause that and how do I get a backup onto my Windows PC done ?