ok, I uninstalled Jazz Jackrabbit while ago because it had some kind of weird error and i could'nt open it anymore. Now, i can't install it anymore. Its because i did'nt delete the registry keys. J2_unist can remove this problem and tell to do like this:

.inf file which deletes the Jazz 2 registry keys if you manually deleted Jazz 2 without using the proper uninstall program. If you did this and tried to re-install Jazz 2, an error would occur telling you Jazz 2 was already installed. This program deletes the offending registry keys so that you can re-install without any problems.
I downloaded it.
but i have a problem: no .inf file! HELP ME!