Why would you need 2 comps with FS2004 when you just can fly together on 1 FS2004??? If you use the right software you can both fly that plane.
Online flying can be done for instance with 2 versions of the commumication software (speak) installed on 2 separte comps running over the network, so you both can speak on the same channel. (but maybe it is also possible to talk on 1 comp just connect 2 mics and 2 headsets on the comp...)
I make a airbus here and i can fly together with the FO. Both can controle the stick when needed and all other things can be used by both.
Frans
www.planesonline.nl