I just tried an uninstall of Mambo and it's not working. After hitting the first button, it says to close to windows and continue witht he removal. After pressing the second button, it's busy for a few seconds then looks like it finishes and stops. I tried accessing my site afterward and it gives a server error "500".
Please let me know when it's ok.
If you can't uninstall Mambo, I believe you will have to delete the folder if its installed in seperate folder. and delete the db used for it manually using phpmyadmin.
You can get 500 error because of few reasons, You didn't post the link to your site for us to check. Go to Cpanel, click "ERROR LOGS", there you will get more info on 500 error. Post that here with your site url.
Well the 500 error has been remedied but Mambo remains. I uninstalled Mambo before using CPanel so I know that's the way to go. I have no problem deleting it myself if advised by the admin or moderators. I just didn't want to screw up something CPanel-related for myself.
I'm currently updating cpanel to the latest version. I hope this will solve your problem.
edit: I meant fantastico