InfoPath Dev

I created several InfoPath forms (that are not browser-enabled), published them to a SharePoint site for several folks to fill out and I've got someone who cannot open any of the forms.  He says it keeps telling him to have the form switched to browser-enabled or open it via InfoPath 2007.  He's got Office 2007.  I just don't understand why it's giving him this trouble.  My guess would be a setting somewhere on his computer, but I honestly don't have a clue.

 Any ideas?

because he doesn't have infopath client installed on his computer. office 2007 doesn't come with infopath.

So, just to verify, you've confirmed he has InfoPath installed on his machine? What happens if he opens InfoPath and navigates to the form template from there - if you give him the URL? It would be http://server/site/doclibrary/Forms/template.xsn -- so the URL to the document library followed by /Forms/template.xsn. When you open IP and navigate to open a form template, you can paste the URL into the dialog for the file path, and it should open the form.