The MSU I'm installing is Windows6.1-KB958830-x64-RefreshPkg.msu, which is the "refreshed" (see: signed with different cert) installer for RSAT for Win 7 SP1. It is one the many updates
redacted by Microsoft, so there is no official public download anymore. Thankfully, the official download link was crawled by the wayback machine, if you need to download it
here.
It takes a very long time (4-6 hrs), but the MSU for RSAT does install successfully, and the various RSAT components appear in the OptionalFeatures list, all disabled by default per usual and waiting to be enabled by the user. Everything is fine up to this point.
The problem is when I go to enable one or more RSAT components by checking their box and clicking OK. The progress dialog appears and churns for a minute, but then an error occurs. The only thing from RSAT I need on this machine is GPMC (enabled via the "Group Policy Management Tools" component), so that is what I have been testing with. Here's what that looks like:
At this point, Group Policy Management Tools is
not enabled and GPMC is thus not available (search for it in the start menu, get nothing). If I restart my computer and open OptionalFeatures again, the checkbox for Group Policy Management Tools is still disabled. If I check the box, click OK, and wait again, it will fail with the same error again. I can then restart my computer, see Group Policy Management Tools is not enabled, and repeat this process ad infinitum with no results.
Attached below is the relevant lines from CBS.log that were generated during Pic #3 in the sequence above.
No lines were written to WindowsUpdate.log during the picture sequence above. That log was flushed sometime between today and when I last (re)installed RSAT several days ago, so there is no residual data left over from installing the RSAT MSU. I could re-install the RSAT MSU to fill out WindowsUpdate.log, but it really does require an entire day to do because the uninstall takes about 1-2 hours and the install takes about 4-6 hours. I can do that if it's necessary, but I hope that the info from CBS.log is good enough for now.