A couple of months ago, I installed the 64-bit version of Debian Linux on my laptop, which is a Dell Vostro 1700. 64-bit linux is stable and well supported these days, so I don't really see any reason why not to use it. After installing the 32-bit compatibility libraries for a couple of programs, I can run anything on it that I could run on a 32-bit linux. So far, so good.
For virtualization, I use both VirtualBox and VMware Server. I prefer VirtualBox, because it works just as good as VMware Server and has a better interface. Still, I also use VMware because of existing VMware images. Either way, since I'm using a 64-bit operating system now, I want to be able to also run a virtualized 64-bit OS. This was initially not working: VirtualBox complained that this requires Intel VT-x, without support for VT-x, the virtualized operating system only sees a 32-bit i686 cpu.
Intel VT-x is a feature that must be supported in the cpu and, sure enough, the cpu in the Vostro supports it. Still, VirtualBox obviously didn't see it. After some hunting on the net, I soon found out that support for this feature must be enabled in the BIOS, and that not every BIOS makes this feature accessible. Even though the cpu in my Vostro 1700 supports it, the factory-installed BIOS (version 00) does not enable it, and --worse-- does not provide the option to enable it. Since the cpu supports it, I hoped that a BIOS update would include this update and started searching on Dell's website. It turns out that Dell actually released several BIOS updates for this model. Even though the info files on those updates don't mention anything about VT-x support, I gave it a shot and upgraded to the most recent BIOS version (07). And, guess what... the new BIOS includes an option for activating "virtualization technology". This is the much hoped for VT-x support. :)
After enabling this in the BIOS, I could run a virtualized 64-bit linux. Nice!