I have been hunting this problem down for quite some time, and in a recent posting you did for Melerland7 (https://www.sysnative.com/forums/windows-update/6263-windows-7-update-error-800f0900.html
) it looks like the closest thing to the same thing happening to me.
First things first:
- Home built hot-rod with OEM Windows 7 64bit - no recovery disk. 3770K, MSI MB, Corsair H2O cooler, memory, and case, OC @ 4.6 (but with Turbo still enabled - idle is a nice low 3.5GHz).
- No backup (Yes, I know - my bad, particularly with OEM version!)
Somewhere after May 15 2013 my Explorer windows stopped opening in the same window. I also received errors while running my flight simulator (MSFT FSX and Real Environment Extreme (REX)) about the Internet Explorer\ieproxy.dll either corrupt or not being correct for this platform.
Internet Exploder... err. Explorer stopped working altogether, and the update logs show conflicts for updates for IE9 (which exists) and IE10 (which I tried to correct the ieproxy.dll problem with). Funny thing: the May 15 update included a patch for IE10 - I did not have IE10 installed!!!
I have run scf /scannow and it generates a ton of messages, similar to those for Melerland7 above.
I have done the IF EXIST modification - nope.
I have done the KB947821 modification - nope.
What did work, to a certain degree, is the "windowsupdate.diagcab" - I don't know what it did, but it seems to be a brute-force little thing that fixed my Explorer window generation problem. It did say that it could not fix the IE9 update problem, and that I have "Cryptographic Services Components are not registered" problem.
IE9/IE10 still blow up/fail to initialize, and I cannot deinstall IE10 (the program removal tool fails) and cannot reinstall IE9 (get a 9C4D error). Attempts to reinstall IE10 yield a 9C48 error. Stuck in limbo...
I have Malwarebytes Pro, Spybot, and Avast Pro running, so I don't think it was a virus (never know, though, do we). I have a suspicion that my son may have interrupted some update process, although the logs don't say anything except that the update failed.
I will happily donate the registration cost of Malwarebytes Pro if you can get me back to a clean state (after which I will do a BACKUP!).
Thanks for the help!