|"if it has two CPUs then only one will be detected"|
Wrong, it depends on the OS. XP Pro supports 2, Win 7 Pro (or better) supports 2, Windows Serever supports 4, 8, 32, or 64, depending on the version.
Info found here: http://support.microsoft.com/kb/888732
And here: http://windows.microsoft.com/en-us/...