Hi J.Y.,
You may want to use the link below to post this in the MS Office Infopath discussion group and explain a bit more on how you'd want
to use the form to help folks understand compatibility in your context.
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Can you make a Infopath 2007 form compatible with Office 2003? >>
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Please let us know if this has helped,
Bob Buckland ?

MS Office System Products MVP
LINKS
A. Specific newsgroup/discussion group mentioned in this message:
news://msnews.microsoft.com/microsoft.public.infopath
or via browser:
http://microsoft.com/communities/newsgroups/en-us/?dg=microsoft.public.infopath
B. MS Office Community discussion/newsgroups via Web Browser
http://microsoft.com/office/community/en-us/default.mspx
or
Microsoft hosted newsgroups via Outlook Express/newsreader
news://msnews.microsoft.com