Do you have Mach connected to the computer via a parallel port? If yes is the parallel port near the top of the computer beside all the other sockets such as mouse, USB etc? If it is then it is likely the onboard port and thus the address set in Mach will likely be correct.
When you start Mach are you choosing the correct profil;e, ie the same one as you attached? If not then you need to do that by either chaging the shortcut to look at that profile or by using the Mach3 loader and picking the profile name in the list.
Hood