Well, it looks like that illegal OEM version has written an entry in the Windows registry. That's good, you can remove that entry then. Here's how:

- Go to the Start Menu, head to Configurations (third or fourth menu from the top) -> Control Panel
- In the Control Panel, double click on the "Software" icon to open the list of programs installed
- Look for "Jazz Jackrabbit 2" select it, then click the "Edit/Remove" button. This will activate Install Shield which will remove the program not only from the hard drive, but from the registry as well.

That's the standard procedure for any program that doesn't come with an uninstall option, but do write register keys.

- JelZe GoldRabbit =:3

P.S. no matter what others say, don't use "regedit" unless as a last resort.