D:\UserTmp\ is an 'odd' location
IIRC calibre portable uses the host systems User TEMP environment variable setting, which is usually set to %USERPROFILE%\AppData\Local\Temp.
Do a start panel search for 'environment variables' and you should be led to this:
While you're there have a look to see if the CALIBRE_TEMP_DIR EnvVar is set, I'm not sure of portable makes any use of that.
BR