I tried calling the above number and a very nice and mostly helpful technician tried to inform me that my system wasn't compatible with a 64-bit OS because msinfo32.exe stated the system type was x86. I have a Intel Duo2 Quad Q6600 CPU in this, how can it NOT be 64-bit compatible? Won't a 32-bit OS ALWAYS report a system as being x86 rather than x64? The best I can tell, the system motherboard was based on the Intel P45-Express chipset and Intel provides 64-bit drivers for that chipset.  The Realtek components of the board also all have 64-bit drivers. I know that OEM builders can modify the base boards somewhat but I find it very difficult to believe they could change this to such an extent that it would run only in 32-bit mode.  Update: I have verified with CPUID utility that this processor does indeed support the EM64T technology. Also, according to other forums, the CPU is the only thing that matters. Should I try calling back again or is there another way to resolve this? Update #2: ***** Last night I tried the online chat and was able to talk with a very nice person called Michael who helped resolve this. I see an order in the system now for the kit, so I'll consider this resolved.
Hello, When we were looking into getting a new system recently I talked to the online support and had specifically asked if I could be sent the Vista Business 64-bit version with the Vostro 420 system I was looking at. I was told at the time I couldn't, and we went ahead and ordered the Vostra 420 desktop. After receiving the system a few days ago I was looking more into x64 issues and such and ran across an article on AnandTech stating that Dell now offers 64-bit Vista to people who ask for it. Searching this forum shows several people who were likewise told that they may receive the 64-bit version of Vista per document DSN ID 158098. Iwould very much like to receive the 64-bit version of Vista Business and ask that one of Dell support from this forum contact me with this information. I live in the US. I've only had the system a few days. I've looked at the drivers installed by the DELL drivers DVD and all of them except one contained 64-bit versions. The one that didn't is easily replaced by a version from Intel's site. I am a freelance tech-support person myself and am willing to deal with whatever issues come from using 64-bit. Thanks, Charles 
Vista 64-bit