From the pcworld article http://www.pcworld.com/news/article/...49,pg,6,00.asp
XP 64 won't have the 32-bit XP's support for DOS apps at all, nor will it run 16-bit apps (but it should have no trouble with 32-bit software)
Does that mean 16-bit compiled DOS apps won't work? Currently in 32-bit Windows 2000/XP, most DOS 16-bit apps run acceptably (provided they do not have specialized video/sound implementations). Is this a result of the Athlon64's lack of support for 16-bit (I don't think so) or is it a time saving move by M$?

Yes, most people don't run 16-bit DOS apps anymore, but I have one or two that are nice to use every once in a while.