Either more files have been created in the root directory than the operating system permits, or more files have been opened than the number specified in the files= setting in your CONFIG.SYS file.
To correct this error
If your program is opening, closing, or saving files in the root directory, change your program so that it uses a subdirectory.
Increase the number of files specified in your files= setting in your CONFIG.SYS file, and restart your computer.