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My CPU is an Intel Pentium D Dual Processor 3.00 GHZ. My system has 8 GB of RAM and is running Vista Ultimate 64 bit. All this info is obtained from the properties page of my system. I have the latest VirtualBox 3.0.4r50677 installed with the latest 3.0.4r50677 extensions. Whenever I try to install a 64 bit guest, e.g. Win7 Ultimate 64 bit, it tells me that I cannot install a 64 bit guest on this platform, but I know it is a 64 bit platform, because I am running 64 bit Vista Ultimate. Confused! What am I missing?

BTW: I am able to install 32 bit guest, e.g. XP Pro, with no problem.

Thanks for an insight,
Charles