can i install IBM Rational Developer for System z on Microsoft Windows
Document Getting Started on PeopleSoft Installation says:
COBOL is not needed for PeopleSoft PeopleTools or for applications that contain no COBOL programs. If your application contains COBOL programs, you need to purchase a Micro Focus COBOL compiler for Windows, UNIX, or Linux platforms, an IBM COBOL compiler for AIX, Microsoft Windows, or an IBM Enterprise COBOL for z/OS and OS/390 compiler for z/OS platforms
Also have a look at this document on Oracle Support
PeopleSoft Enterprise Frequently Asked Questions About PeopleSoft and the IBM COBOL Compiler [ID 1211907.1]
As the name says IBM Rational Developer for System z is for IBM zSeries, which is if I am not mistaken mainframe. This will not work on Windows.