How to remove/disable old themes?

We recently upgraded our RT to the latest version (5.0.1) so old themes like web2 no longer work.

How can we go about disabling these old themes so users can only select from the new elevator themes?

Thanks,
Michel

Solution:

Remove the theme directories from /opt/rt5/share/static/css/

Did you upgrade RT 5 in the same directory as RT 4?