Location of registry entry for Windows backup drive identification

I'm running Win 7 Pro 64bit and am a gamer. I keep all my games on my E: drive (2 TB) so they don't interfere with Windows on my C: drive (500 GB). My backup drive is 1 TB.

A while back I was installing a game and noticed that it was also installing MS .NET framework on my E: drive. The next scheduled System Backup failed and the error stated there was no space on my backup drive for a System Image.

Wondering why a 1TB drive couldn't backup at 500 GB drive I noticed that, in the system backup configuration panel, it stated that, along with my personal files, Backup would also make a System Image of the C: and E: drives. No wonder the backup failed.

I uninstalled the game that installed the .NET framework but the damage has been done. Unless I physically remove my E: drive, in which case Backup only shows the C: drive for System Image, Backup will try to image C: and E:.

I deduced that, with the E: drive uninstalled and Backup only showing the C: drive for imaging, but both for imaging if the E: is installed, that there must be some registry entry showing which drives Backup needs to image.

If I can edit this entry to only reflect the C: drive, with C: and E: installed, that would save me from having to remove E: every weekend to do backups. Luckily I have a case where I can flip a lever and pull out individual drives but in order to do so, I have to shut down Windows and power off the system. Editing a registry entry would save a lot of time.

There's got to be an entry somewhere (I tried to look but never found anything under entries associated with Backup). Does anyone know?

You might look at
Can I back up Windows 7's backup settings? - Super User

But won't restoring the image from before E: was included take care of it?
That's how I'd do it.

Sorry for the late reply - we were out of town.

The 'install of .NET' on the E: drive happened quite a while ago and any backup of before that has been over-written.

Somewhere it has to be written what the backup program will be backing up. If I remove the E: drive and enter backup configuration, any reference to the E: drive is not there. I install the E: drive and the reference is back, so 'something' is writing 'something' 'somewhere' and, unless it's dynamically written into a running system program (which you can't edit), I would think that you could find some entry and change it.

Any ideas?

I deleted the reg key in the link above after setting up backup and creating an image.
When I reentered backup it was a blank slate. Unfortunately trying to do another image resulted in an error - it wouldn't take an image. I didn't back the key up, so I can't fool around with it until I do my next restore.
You might try backing the key up, and editing/deleting the values until it works.
Can't say what the values are because only the destination drive is apparent.
I'd try removing all values in the subkeys, - instead of deleting the entire key as I did.
If it breaks backup, just restore your saved key.
Do this at your own risk.
Really though I'd not use Win 7 backup. It has "issues."