The discussion on 64bit is actually endless! But the reality is that it still seriously lacks support by too many manufacturers and software companies. When you look at the latest pc game out just look at the system requirements that will probably say Vista, XP, 2000. That would be the 32bit versions of both XP and Vista there.
One claim by Microsoft is a degree of backward compatibility for older versions in order to allow some older softwares to run a newer version. Being that it has taken a full 6yrs. just see Vista 32bit appear and XP Pro 64bit has been out only a few the mainstream is still 32bit orientated.
In the final analysis if you can call it that the actual trend to 64bit will take quite a bit longer then seen when the 16bit Windows 95 was replaced with the 32bit 98. NT 3.1 was already one 32bit version out at that time. The 32bit version of the next version of Windows will be out reportedly in 2009 going by the name of Vienna.
The 32bit versions of XP see the option for running programs in the 9x-ME, 2000 compatibility mode. Often that doesn't work for much there. The best advice if you decide to try out a 64bit edition would be to dual boot it as a secondary not primary version to see how things go from there. Since the market place is still 32bit the word would be look before you leap in some sense.
