I've built a clean MOSS development environment deployed an InfoPath form using Sahil Malik's technique of wrapping it up in a feature and leveraging the Receiver Class. Works great. It seems to register the form as a fully trusted form.

I then add the generated content type (same name as form) to a Form Library and force it to open in web page. Then I select New | My Form in List View Web Part and get this error:

The form you are about to open supports digital signatures. You must install the Microsoft Office InfoPath Digital Signature Control to be able to digitally sign this form. Do you want to install the signing control?

So I click Yes and get

And then tick 'I accept' and click Next and I get a nice Internet Explorer - Security Warning!

And I don't blame it with a name like $(loc.IPFS_DSIGRES_CABNAME)!

SO I click Install button and wait for something to happen and get this:

Yet another warning about dsigctrl.cab so I click install again.

This then displayed the InfoPath Form in all it's glory in web mode. I wonder whether there is a way to set this up on farm so that the first user doesn't get this...or is this the only way...to deploy a form like this and run through this so someone doesn't have to?!?!

It's kind of walked through in this lab, but it's still a manual process for the form.