public class mmWizardForm : mmBusinessForm , ImmWizardFormIncidentally I had a bit of trouble adding the replacement DLL to the GAC and to my project. At first I got a duplicate in the GAC, then could not deleted the installed MMNet winforms dll without deleting (or renaming) "C:\WINDOWS\assembly\GAC_MSIL\Mere Mortals Framework Windows Forms 2005\2.4.0.0__57ceb69243304587".