Service Pack 1 Install Failed Error 8024200D

Umm, dunno
The only think I can think of at this point is to see if there's anything to back out of...

You'll need to boot to the Repair Environment -as soon as the machine restarts, start tapping F8 - this should bring up the Advanced Boot Menu, at the top of which should be the option 'Repair my Computer'
Pick that
You'll have to log in with your username and password.

Pick the option to use a Command Prompt
At the prompt type

dism.exe /image:C:\ /cleanup-image /revertpendingactions

This is supposed to revert all pended updates.

post back with the result

I suggest repeating the Repair Environment command - this time using the following command instead...
dism.exe /image:D:\ /cleanup-image /revertpendingactions

Go for it - do a Check for Updates first.

Well, the check for updates found the service pack, but the installation still failed, with the same error code after only about 3 minutes of waiting time. I am puzzled here. Anything else you can think of? Other than the time it takes to reinstall any and all software I have on my computer now, I have worked out that I would not lose much at all from a clean install of Windows 7 Pro. I would rather not do that if possible, purely because it would take awhile, but it is my backup (no pun intended, again) if we can't find a solution.

(EDIT) I haven't slept in awhile, so I will go do that now. Thank you guys for your help, and if you have any more ideas, by all means, post them and I will try them when I get back.

The only other thing to try is a repair install, if you have the media - I'm out of ideas now

I have a long shot idea. Could you post one of these using this tutorial by Golden.

Disk Management - Post a Screen Capture Image