Hi,
If you are using infopath2007, then you have one option to open the form as Webpage.
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Go to the Tools -->Form Options
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Select "Compatability" tab.
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Select "Design a form template that can be opened in browser or infopath" chack box
Make sure you need to publish this form to Sharepoint 2007.
After publishing to the Sharepoint server, you need to check the "Display as a Web pag" option in the Advanced proprties in the form Library. Then, Form will be opened in Webpage even that machine have Infopath installed.