How do I remove the "Undo" option from Windows' right-click context menu?

Here is a hack which might do what you ask for, but is somewhat risky.
I have not tested it, for obvious reasons, but it might work.

1. Download and install Resource Hacker
2. Go to C:\Windows\en-US and take ownership of (if required) and then copy the explorer.exe.mui to somewhere safe. If you are running a 64-bit system you should also modify the explorer.exe.mui which is located in C:\Windows\SysWOW64\en-US. To find all the copies: Go to Start Menu and do an extended search for explorer.exe.mui. You will need to repeat the procedure for each of them. If you have no success with saving the files you will also need to take ownership of the containing folder.
3. Open your explorer.exe.mui(s) in Resource Hacker and navigate to Menu / 205 / 1033 :
4. Select and delete the Undo line
5. Press Compile Script and save
6. Go to your original folder(s) again and rename your original explorer.exe.mui file(s) (explorer0ld.exe.mui?) then copy and paste your modified explorer.exe.mui file(s) into place.
7. Go to Start Menu / Run and execute mcbuilder.
8. Once the window closes, restart your computer.

I take no responsibility for the result of the above or their effects. I suggest taking good backups first and creating a system restore point, just in case.