I've tested with Windows 7 SP1 64 bit IE 9, result:
We have made our best guess at detecting your operating system and have determined it to be: Windows 7 32 bit
If this is correct, download your VIA client here:
VIA Installer (Win32)
However when I test it with the IE 9 64 bit version, it's OK and gives me Windows 7 64 bit.
But in my opinion it should detect the OS architecture, not the browser which could be 32 or 64 bit on a 64 bit OS.