ITNinja

I have tried installing Mathematics by using the aforementioned msiexec commands (from an Administrative command prompt):

 msiexec /I MathematicsAddIns_x64.msi FROMSETUP=1 ALREADYRUNNING=0 DOTNET35=1 WORD=1 ONENOTE=1 /qr

msiexec starts to run and works perfectly until it gets to 'Writing system registry values' at which point I am given the following error message.

"Could not write value AdminDisableSxS to key \Software\Microsoft\Mathematics\Standalone\4.0. Verify that you have sufficient access to that key, or contact your support personnel."

I have tried this on two separate machines, both running Windows 7 x64, one a fresh install and one existing installation.  If I run setup.exe and follow all of the prompts, Mathematics installs fine so the msi is clearly missing out on something but I can't figure out what...