We got 2 servers on same network, Server-A and Server-B.

On Server-A (widows server 2003), we have IIS 5.2 and our website was hosted on it few month ago (about 7-8 months).

We bought a new server, Server-B (Windows Server 2008) with IIS 7.5 and copied our old website on this new machine. On our router, we forward the port 80 to Server-B.

The Server-A is still on because we need to access some old data by our old website. I would like to access it with it's internal Ip (192.168.1.xxx/mywebsite)

On my Windows 7 computer, if I write www.example.com or example.com (without www.), I'm being redirected to Server-B and I can see our new interface.

On some Windows Vista computer, example.com (without www.) redirect to Server-B, but if I write www.example.com, I'm still on Server-A. In our website code (on Server-B), we sometimes redirect with a "www." so this is causing some error because we are trying to access a webpage that exist on Server-B but not Server-A and because the www.example

I compared 2 computers with Vista Home on them and Internet Options looks the same. I cannot figure why this is happening