At compile time, this error occurs when include files are
nested more than five levels deep.
 
At run time, this error may occur because:
   ■ BASIC has a limit to the number of disk files that can
     be open at one time. This limit is a function of the
     FILES= parameter in your CONFIG.SYS file. Increase
     that number and reboot.
   ■ The operating system has a limit to the number of
     entries in a root directory. If your program is
     opening, closing, and/or saving files in the root
     directory, change your program so it uses a
     subdirectory.