Hello jrball,
For good measure, please first check that you're using Hauptwerk v5.0.1 (not v5.0.0) via 'Help | About Hauptwerk'. (v5.0.0 intentionally kept a larger proportion of the RAM unused by Hauptwerk, to help guard against system instability, but for v5.0.1 that proportion was made smaller so that people can fill the RAM more fully at their own risk. With v5.0.1 on a system with 48 GB, Hauptwerk would only keep 2 GB unused, so if it's reporting 42.3 GB 'free', which is less than 48-2=46 GB, then 42.3 GB is how much RAM Windows is reporting as 'free'.)