Do you get this when you do the install? a message it will not run on the operating system? If so go to the file rt. mouse on the setup.exe file and under compatable tell it to run in win98/me mode (don't remember if nt mode worked). Should work fine and save you money to start with.
we had the same thing happen when xp 1st came out. and had to do that with autodesk 2000i LDD2, which is the civil design acad, only cost 5,500 at the time. now we use Civil 3d 2006 at 8,500 a pop.