Hi Crowface, This should help.
First, make a backup of your hard drive, just to be safe.
Next, try the following one-minute, one-line MSI-error fix.
It deletes the Registry item that contains the data from a broken or unfinished MSI run.
Open an admin-level Command Prompt window.
Now, type (or copy/paste) the following long line into the command window:
reg delete HKLMSOFTWAREMicrosoftSQMClient WindowsDisabledSessions /va /f
Press the Enter key then close the Command Prompt window.
Reboot your PC to make sure you’re getting a fresh start.
When you restart, the unfinished or broken installation Registry data should be gone,
allowing you to update normally.