It could have changed a number of things, impossible for us to tell what
kind of damage it may have wreaked on the workstation.  Most of these
Registry destroyers, er... I mean registry "Optimizers" keep a backup of
the "fixes" so that the system may be returned to its previous state.
Check in the program and see if such a restore feature is available.

As you have already found out most of these "Optimizers" cause more harm
than good and should only be used by experienced users and under limited
circumstances.  Certainly average users should not be installing these
kinds of dangerous tools in a corporate environment, perhaps they have
too many permissions or privileges on the workstation.

John