Would everything to do with installation be on the D:drive
No. MC registers components with Windows, and those components are specific to the 32 or 64 bit versions.
Just install both on the C: and NEVER run them both at the same time. That includes the Media Server. If you shut down the 32bit version to switch to the 64bit version, make sure that the 32bit Media Server (if you run it) is also closed down. Same going the other way. The 32bit version will be installed in the /Program File (x86)/ directory, while the 64bit version will be installed in the /Program Files/ directory. They will share stuff under the /Users/ directory, including the library, and that is fine.
Also, when you change from one version to the other, expect Windows UAC to ask if it is okay for MC to change your system. Tell it Yes every time. MC is registering the correct version of components when this happens.
Once again, just minutes behind you Jim.