Try mo palitan manually into original file extension using cmd o command prompt.
Open command prompt
Type cd/ (hit enter)
Type f: (example chk file located in local drive name is F) hit enter
Type cd folder_name (Folder name kung nasaan yun .chk file)
example: F:\>cd folder_name (hit enter)
Then type ren *.chk *.jpg (Yun chk file papalitan mo ng original file extension na example .jpg .png .mp4 .mov etc. )
example F:\folder_name>ren *.chk *.jpg (hit enter and check mo kung nachange na sa original file extension)
or if it doesn't work use chk software recovery
Code:
http://www.techcrawler.de/dechk/index_en.html