First when I try to change "form properties" to I get this error...
The form cannot be configured to send results via email. The website may be located on a disk based server or on a server that has not been configured to send email. Contact your systems administrator etc. etc.
I recently put a feedback form on my site and was getting the exact same error message, but it didn't prevent the form from working correctly. Are you creating the form on your computer and then publishing to LP? That is what I was doing, and I think the error message refers only to the copy of the form on your computer. In other words FrontPage is telling you that as it sits on your computer, it can't send e-mail. But once you publish the site, and it is sitting on the LP servers, everytyhing should work fine. At least that is what I found.
Also, have you gone through the FrontPage forms tutorial? I found that to be very helpful too. I just followed the tutorial and ignored the error message when I created the form. It worked fine when I published it.
Hope that helps.
Ron