OK, I understand about running RSAT on the Win7 PC, but it still doesn't explain that there is no way (that I can see) to import the new features of Windows7 into a 2003 server GPO.
If I do a gpedit.msc on the W7 PC it brings up the updated local GP, and I can see features like Desktop Gadgets (under User Config> Admin Templates> Win Components). But in Group Policy Management, those new options aren't available.
I tried the Vista options suggested above, and also searching for adm files on the Win7 PC. But both of those options only have admx/adml files.
I know when I upgraded to Office 2007, Microsoft had a package that contained the adm & admx files so I could add the new features into the server GPO. Seems to be missing for Windows7 so far.