If you didn't backup the div.exe file before using the no-CD hack, try re-installing the patch to replace it (assuming you have a CD version of the game). Most of the time just reloading the save before hitting the gong and doing that part again with the play CD will work, but a couple people reported having to re-install the game (though the patch should be sufficient).
If you have the DVD version of DD, you will either have to reinstall the game or see if you can manually extract the original executable (don't know if the files on the DVD are predominantly in rar files, like the CD version, or not).
see
Troubleshooting Tips (& manual install procedure)