I am hopeful this helps someone now or in the future who is going through what I just went through.
Problem: Instaforms Invoice and Estimate Pro version 2.0 running on Vista 64. I downloaded the patch from the developer Nova Development to make the application operable on Vista. It updates the PDF converter and its driver. But, you may be frustrated that you can not produce pdf or use the email function. Here are the solutions (Finally!)
1. First make sure that you have the latest ADOBE version
2. Second, go to the control panel and open up the printer section (labeled printers and faxes in classic view)
3. Right click on the pdf printer ( in this case it is "I&E Printer") and click properties
4. On the ADVANCED tab you will see a drop down menu for the drivers. Make sure that it is selected to AMYUNI DOCUMENT CONVERTER 2.51
5. On the ADVANCED tab make sure the you uncheck the SPOOL button and check the 'Priint directly to the printer' button
6. On the PORTS tab (this is the most important one and gave me the relief I needed!)
Either select the already created LOCAL PORT named 'NUL:' and hit apply. If this port does not exist click create new port, select LOCAL PORT and name it 'NUL:'
This will enable you to create PDF and use email.