Open the registry, locate HKLM\Software\Microsoft\Windows\CurrentVersion\uninstall. Serach under that key for the name of the 'remove' entry you want to get rid of. It should be found as a DisplayName value. Then delete that whole subkey of Uninstall.
If you don't understand the above, don't try it.
You will no longer be able to uninstall the relevant software without the original install disks. And even maybe then not.