Since it is for Ganymede (eclipse 3.4), I would advise to uncompress the zip in the dropins in the HibernateTools-3.2.4.Beta1-R20081031133 directory created after the name of the archive.
Once it is done, create in the [eclipse\dropins\HibernateTools-3.2.4.Beta1-R20081031133]
an 'eclipse' directory, in which you will move the plugins and features directories creating at the extraction of the files of the archive.
Add a .exclipseextension in [eclipse\dropins\HibernateTools-3.2.4.Beta1-R20081031133\eclipse]
:
name=QuickRex
id=org.hibernate.eclipse
version=3.2.4b1
So:
eclipse
dropins
HibernateTools-3.2.4.Beta1-R20081031133
eclipse
.eclipseextension
features
plugins
Relaunch eclipse and the plugin Hibernate should be detected.
If you install another eclipse, just copy the content of your dropins directory to the new eclipse\dropins
and your set of plugins will be detected again.