Hi Neil,
As far as I know, InfoPath 2010 offers 5 form types for compatibility with the latest and previous versions of InfoPath:
- Web Browser Form
- InfoPath Filler Form
- Web Browser Form (InfoPath 2007)
- InfoPath 2007 Filler Form
- InfoPath 2003 Filler Form
If you have created a if you have created an InfoPath 2010 form, you can go to
File > Info > Form Options > Compatibility and try changing the
Form type to the InfoPath 2007 form, and then test if it can be edited using InfoPath 2007.
Since your question is InfoPath related, if you need further assistance on this issue, I'd recommend you post a new question to the following forum:
https://social.msdn.microsoft.com/Forums/sharepoint/en-US/home?forum=sharepointcustomizationprevious
The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their
knowledge or learn from your interaction with us. Thank you for your understanding.
Steve Fan
TechNet Community Support