Some time ago Peter Loft Jensen wrote about how to easily give a user account the neccessary permissions to access the IIS metabase & required directories, and thus be used for running the IIS process.
We’re running all x64 servers, but our IIS is running in 32 bit mode due to some non-x64 compatible 3rd party libraries. Usually this means we have to use the Frameworkversionaspnet_regiis.exe bin instead of the Framework64 version - otherwise it might interfere with our 32 bit IIS settings.
Doing that resulted in the following error:
The solution was quite simple, it seems you must use the x64 version on an x64 system to run the -ga command. After using the binary in the Framework64 directory, the command ran perfectly.