@AscendedDescent
Fully close out of your IMVU client, so that it is no longer running. boost_pythod.dll is one of the IMVU client files. Preparation exe can not access the file if it is currently in use by the IMVU client.
If you continue to get the error message even after closing out of the IMVU client, then check your windows task tray to make sure it is not still running as a background processing. You might have to right click the IMVU icon in your task tray and close from there.
If you still get the error message, then restart your computer to make sure allocation of the file is not deadlocked.