If you have Quattro Pro then the *.trn file is a translation support file. No reason for you to open it. If you leave it where you find it then the program will find it. If it is in the C
directory then I would guess it is a legacy application.
The pdoxusrs file is almost certainly a Paradox database file. Are you sure that there is no extension?
The *.tmp is most likely a temporary file that was not cleaned up by the application that created it because of an abnormal termination. Again, if it is in C
then I would guess that it was created by a legacy application.
The config.old is most likely the previous version of your config.sys file. I suspect that a legacy application rewrote the config.sys and saved the original as config.old (which is an old windows3.x practice.) You can check to see if the time stamp on your config.sys is newer than the other system files in the c
windows directory. This conjecture, however, is not consistent with opening difficulties since the file should contain nothing but ASCII text.
The only scandisk file that I can think of that might be in the C
directory is the scandisk.log log file. Again, that should be editor-readable.
I'm with fobotcso - can't imagine why you are trying to open these files. On the other hand ever since win3.x I have been urging the developers within earshot that their applications should on installation create an inventory of all installed files with time stamp and file size.