But now that I got the full version, it can't be selected because it is not there.
That's really odd as the license portion of the program has nothing to do with the preset list under "New Bodies".
I'm still not sure why this happened.
Uninstalling is safe. So is deleting the folder:
c:\program files\universe sandbox\
You can always re-download the setup file if you need to and install it again.
And reinstalling or uninstalling doesn't touch the files here:
(My) Documents\Universe Sandbox\