It is much simpler to create an environment variable for your Access program to use. Computer->properties->Advanced->Environment Variables.

Under system variables New -> enter a variable name and value (i.e. "VISTA")

My variable is "Windows" and the answer is "Windows XT" or "Windows VISTA". As a switch between two diff computers with the same files and database (USB drive) occasionally some code needs to know which system it's on. This works well because the variable is specific to the computer not to the database.

It'd been more elegant if MS would allow you to just edit the "OS" variable.