Hi,
I had the problem of of being unable to install Flight Simulator X on Windows 8 64-bit (Error 1628) tried all the suggestions here but none of them worked for me.
Then looking online for a solution found out that windows 8 has a
hidden Administrator Account with extra privileges.
Thought I would give it a try by enabling this account that is not enabled by default as really wanted to play this game after playing the demo.
And it worked! no more
Error 1628 when installing the game using the hidden Administrator Account.
Here is the link to the page on how to enable it:
Windows 8: Enable the hidden Administrator Account - gHacks Tech News
Hope this works for some of you let me know how you get on.
Ady.