IRM Restrictions

I am running Windows Vista and Excel 2007 and trying to set up a file so that it cannot be copied, forwarded, and expires after a certain time period. In the help section it says that Windows Vista should come with the IRM under SP1, but I don't have the ability to 'Restrict Permissions' under the 'Prepare' menu. Any ideas how to turn this feature on in Excel 2007?

Thanks!
Nate