Windows XP Pro 64-Bit and NAV2009 Issues

I purchased a 2-year, 3 PC license from ebay for an excellent price.  I've successfully installed one licence on a 32-Bit Windows XP Pro unit and it's working and updating fine.  However, when I try to install the trial version on my 64-Bit PC (Win XP Pro x64,) I receive a "can't not install on this OS" error message (not near the PC for the exact verbage.)

 

I'm confused.  I thought NAV 2009 was 100% 64-bit ready.  I've used the installer package from Norton.com and Download.com with the same reasults.  Is there a special installer that I need?  Does this not happen on a full Retail disk build.

 

I contacted the buyer and he said it's only compatible w/ Vista 64-bit.

 

Any help will be greatly appricated.