I was trying to install Windows 7 updates on a 32-bit Asus Eee PC. Repeated tries had brought me to a standstill: a few incremental successes along the way, but now I was just consistently getting this:
Windows UpdateClicking on the "Get help" link opened a general-purpose help dialog with eight different possible solutions. It was not clear which one I would need. I put that on hold and consulted a previous post in which I'd had a similar problem in Windows XP. That effort had failed, and anyway that was a while back. I did a new search. That led to advice to go into Control Panel > Programs and Features > Microsoft .NET Framework 4 Client Profile > right-click > Uninstall/Change > Repair. When that was done, it needed to reboot. After rebooting, I went back to Windows Update and tried again. That was the solution.
Some updates were not installed
Failed: 6 updates
Review important updates
Code 66A: Windows Update encountered an unknown error. Get help with this error.