MFCOBOL Compiler on VISTA

I have a Microfocus COBOL 4.5 compiler which runs fine under 2000/XP under DOS Shell, but refuses to run under VISTA.

I get a " is not a Valid Win32 Application" error message. I am trying to compile my COBOL programs giving DOS command from prompt COBOL . It gives error while executing COBOL.EXE. All COBOL programs gets executed correctly and application runs very fine, But i cant able to compile the program after modification. Kindly help me with solution.