[chaley]

I don't have that folder.

I did some googling for cali_core4 and it does seem that it contains calibre code and DLLs. I didn't try to work out why, but I don't think it is reformat. It looks more like some other packaging of calibre.

The site https://www.advanceduninstaller.com/...pplication.htm contains instructions on how to uninstall calibre 4.6.0. The equivalent instructions for other calibre releases do not mention cali_core4.

Spoiler:

AppData\Roaming\cali_core4\cali_win\app\DLLs\calib re-eject.exe
AppData\Roaming\cali_core4\cali_win\app\DLLs\calib re-file-dialog.exe
AppData\Roaming\cali_core4\cali_win\app\DLLs\calib re-launcher.dll
AppData\Roaming\cali_core4\cali_win\app\DLLs\cjpeg-calibre.exe
AppData\Roaming\cali_core4\cali_win\app\DLLs\jpegt ran-calibre.exe
AppData\Roaming\cali_core4\cali_win\app\DLLs\JxrDe cApp-calibre.exe
AppData\Roaming\cali_core4\cali_win\app\DLLs\optip ng-calibre.exe
AppData\Roaming\cali_core4\cali_win\app\resources\ calibre-ebook-root-CA.crt
AppData\Roaming\cali_core4\cali_win\app\resources\ calibre-mimetypes.xml
AppData\Roaming\cali_core4\cali_win\app\resources\ calibre-portable.bat
AppData\Roaming\cali_core4\cali_win\app\resources\ calibre-portable.sh
AppData\Roaming\cali_core4\cali_win\app\resources\ content-server\calibre.appcache
AppData\Roaming\cali_core4\cali_win\app\resources\ content-server\calibre.png

My guess is you can delete it.