I need to test my software on a variety of 64-bit Windows versions. I hoped I would be able to use Microsoft Virtual Server, which I've been successfully using for a while for 32-bit tests (including German, Russian and Korean flavors of Windows - quite a feat for a Ukrainian with English as a second language), but to no avail - at this point even latest MS Virtual Server is unable to host 64-bit guest operating systems. So despite enjoying being lazy, I was forced to check out free VmWare Server. I hoped to run it on my main Vista x64 dev box, but VmWare Server did not install correctly on Vista x64. That was quite a setback for my product delivery schedule, because I realized I needed another box with 64-bit Windows 2003 Server on it to be sure I could run VmWare Server. I dug through my closet with PC parts and after combining what I had with $200 worth of parts bought from NewEgg.com I had a modest 64-bit box with Pentium D 805 and 1GB of DDR memory. VmWare has installed without a problem, but when I attempted to install Windows XP x64 VmWare Server told me that my Pentium D CPU is no good because when it comes to Intel CPUs, 64 bit guest OSes can run only on EMT64 units with Virtualization Technology (VT) support! Fortunately, my dev desktop had Core 2 Duo E6300, which does have VT support, and both Pentium D and Core 2 Duo use the same LGA 775 package, so I was able to simply swap CPUs and ta-da! - after that VmWare finally started cooperating and is installing XP x64 guest OS as I'm typing this article.
Conclusion: If you want to run 64-bit guest OS in VmWare using Intel CPU you will need a box with a processor supporting Virtualization Technology, and run Windows 2003 x64 as a host OS.