Because it's a 16-bit compiler designed for MS-DOS in the 80s? Grow up and use a modern compiler, or stop whining and downgrade your OS to something closer to the Turbo C era.
p.s. For those of you who are tempted to chime in that Turbo C can be run successfully on Windows 7, stuff it. It's well past time for Turbo C to die, so put away the defibrillators and let it go peacefully. The longer we cater to stupid people trying to use compilers from the age of shoulder pads and slap bracelets, the longer it will take for legitimate advances over the last twenty years to be adopted.