Microsoft has recently announced that Dynamics NAV (Navision) is now fully supported un Windows 7.

The following versions of Microsoft Dynamics NAV are compatible with Microsoft Windows 7 and Microsoft Windows Server 2008 R2:
• Microsoft Dynamics NAV 2009 SP1
• Microsoft Dynamics NAV 5.0 SP1 with Platform Update 2
https://mbs.microsoft.com/public/insights/ReadArticle.aspx?rcpt_id=17058606&ja_id=49072

Note that versions prior to these are not fully compatible (although we can assist with work-arounds) and that we would recommend you upgrade to the newer versions to take advantage of all the newest functionality.  Here is a posting on the latest NAV 2009 release HERE.