I'm not an 'engineer' -- I'm not sure I've ever ridden in a train -- but I do have an answer. Here is an easier method that doesn't disrupt permissions or file ownership; you can put mspaint.exe and mspaint.exe.mui anywhere at all; it doesn't matter where
you put them, as long as you put mspaint.exe.mui in an 'en-US' subdirectory of where you put mspaint.exe.
For example, I put them in C:\Program Files. Mspaint.exe went in C:\Program Files\Paint Vista, and mspaint.exe.mui went in C:\Program Files\Paint Vista\en-US. Then, I made a copy of the Paint shortcut in C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories,
renamed it to 'Paint Vista' and pointed it to C:\Program Files\Paint Vista\mspaint.exe.
1. Make a directory called C:\Program Files\Paint Vista.
2. Make a directory called C:\Program Files\Paint Vista\en-US.
3. Copy mspaint.exe from C:\Windows\System32\ in Windows Vista to C:\Program Files\Paint Vista\ in Windows 7.
4. Copy mspaint.exe.mui from C:\Windows\System32\en-US in Windows Vista to C:\Program Files\Paint Vista\en-US\ in Windows 7.
5. Go to C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories.
6. Make a copy of Paint.lnk in this same directory and call it 'Paint Vista.lnk'.
7. Right-click > Properties > Shortcut > Target > "C:\Program Files\Paint Vista\mspaint.exe".
Why in the world does Microsoft put paint in the System32 directory? Who knows. It's definitely not a system file, so it belongs in 'Program Files' anyway.