Fix C000009A Error on Win 7 SP1 Install

Problem :

Have tried this on 5 machines today - got the C000009A error on 2 of them - the only fix seems to be the DISM revert command shown in this thread. All 5 had ALL language packs installed and where fully up-to-date with all Windows Update fixes prior to the install. The 2 that failed where a brand new i5-based HP laptop that was a clean win64 ultimate install, and a core i7 gigabyte x58 mobo loaded up with 5T drives and 12G ram also a win64 ultimate machine - been running fine for a while. 2 other machines, both i7-920 x58 gigabyte units running win64 ultimate w/all language packes installed, took 12 hours to get 1/2 way thru the progress bar - "cancelled" at 12hrs - hopefully they will succeed at cancelling...;) 5th machine is a ibm/lenov TP 410 core-i5 laptop - cancelled after 10 hours at 1/2 complete. That's 0 for 5;) Guess I'll wait for a bit before attempting this again.

Solution :

1. Do a normal shutdown and then bring the system back up;

2. Go to Start and right-click on Computer. Then click on Properties. If you see (4th or 5th line down) Service Pack 1, then you are done. Presumably you will not see that line.

3. It is the Language Display packs that create the problem.
Go to Start, Control Panel, Region and Language > Keyboards and Languages > Install/Uninstall Languages > Uninstall display languages. Then click EVERY language there, except English. Then uninstall. This process will take about 1 hour, maybe longer.

4. Your computer will probably reboot after this process is finished, but if not, do a reboot.

5. Go to Start, Control Panel, Windows Update. You should see SP1 still listed there. Click on it and install it. All (or most) of the files that SP1 needs for its configuration are already in place from your earlier failed install, and the installation will go faster than the first time. The process does have (heart stopping) pauses, where it seems that nothing is happening, but just be patient and let it go through its paces. The system will reboot when the blue line is all the way to the right, and Windows 7 will come up, and will continue to configure SP1, so it is a slow process.
You will, however, not see those fast-moving lines: "Applying update operation nnn of nnn" until an error stops the process, but instead there will be a "nn% complete" display. Let it do its thing without interference. This also will take some time.

6. You may confirm that you now have SP1 installed by repeating step 2 above.

7. You can now also re-install one or more display languages by repeating step 3, and after clicking on Install/Uninstall languages, install the languages you need.