I know there are more than a few companies out there that are still needing to run legacy software 10 or more years old that are sticking to old versions of Windows just to make sure they software still works. There is always the option of running an old OS in a VM, but there are huge security risks in doing so especially if the system needs to be connected to an IP network. Most of these legacy applications rely on 16bit computing and the past half decade, Microsoft has been moving from 32bit computing to 64bit computing. Many industry market share surveys show that the 64bit versions of Windows 7 dominate the marketplace. This is why it had been rumored that Microsoft was not going to create a 32bit version of Windows 8, but they most definitely are making 32bit Windows 8. What was unclear was if 16bit computing could still occur inside the Windows 8 32bit. Microsoft's Building Windows 8 Twitter account has a post that does clear this up. 16bit applications can run on the 32bit version just not the 64bit version (and the same remains true for Windows 7)
This is just another reason to update to Windows 7 or Windows 8 when it is released. Just be sure you are utilizing the correct version (32bit or 64bit) for your purposes.