i've 12gigs of data in .CHK extn which r generated from cross-linked files. how to get back these CHK files?

one day when i booted my machine, some folders and files had turned into junk characters from their original name. i was not able to access to those folders or to the files. when i re-booted the machine, it automatically started to scan for errors. it converted all my files into .CHK files and dumped them in a directory. there were a lot of MP3s, MPEGs and some huge files, now i am not able to open any file even if i change the extension. i need help.