You've found .CHK files (FILExxxx.CHK) on your disk. Cause: CHK files may be created when Chkdsk or Scandisk needs to delete (parts of) files in order to return the filesystem to a consistent state. Solutions: CHK-Mate can determine if CHK files contain usable data, like for example Word documents, ZIP files etc. If a known datatype is found, the CHK file will be copied to a file with the correct extension. CHK-Mate recognizes the following file types by default: JPG, GIF, ZIP, CAB, EXE, DLL, OCX, WRI, BMP, DOC, PPT, XLS, PDF, HTM(L), WAV, MID, AVI, RAR, TIF and MP3.