Switching to Windows 7 with NIS 2009

I am presently running Vista with NIS 2009 (3 PC license).  I would like to do a clean install of Windows 7 on my machine and continue my NIS 2009 coverage.  It is unclear to me how I do this.  Once I complete the install of Windows 7, I suspect that if I attempted to install NIS 2009 off of the original disk, the install would fail.  Will I be able to download a newer, compliant, version of NIS 2009 from the Symantec website as a registered user?  And if I can do so, will it be counted separately against my 3 PC license, or as a repeat of the same PC?