I have created some custom forms for a Sharepoint 2007 list using Sharepoint Designer 2007. When I attempt to "install" these by opening the list properties dialog box in SPD, it appears to accept the change. I select the appropriate content type, browse to the form file and then click Apply. The new form appears in the dialog, but when I close the dialog and re-open it, the original form has been reinstated. No errors are thrown. I'm a site collection administrator so I think I have adequate rights. Any suggestions would be greatly appreciated!
I've experienced this before in 2007 and sometimes it just didn't "stick". The process I found that worked more consistantly was to make sure the new form was not open in the designer when going through the dialog options to set the new NewItem form.