I would suggest you just buy several flight sims and try them out. You should be able to pick them up cheap at EBGames B&M, titles like European Air War and IL-2 can be had for around 10-20 bucks or so. I know both games support LAN play and IL-2 has the cooperative mode as I mentioned above. Search google for some reviews if you want to see the strengths/weaknesses of each game.
Another option you may want to consider is to pick up a copy of Motocross Madness (1 or 2) or Mechwarrior. Both fun LAN games played with a joystick. I believe MM only requires the CD in the tray to start the game and MW has a certain file (search google) that can be used to play the game with no CD. I only condone this for personal use on a home LAN so you don't have to make backup copies to start each computer, not to share copies. Both games are older so should be able to be found cheap somewhere.
Have fun!!
Another option you may want to consider is to pick up a copy of Motocross Madness (1 or 2) or Mechwarrior. Both fun LAN games played with a joystick. I believe MM only requires the CD in the tray to start the game and MW has a certain file (search google) that can be used to play the game with no CD. I only condone this for personal use on a home LAN so you don't have to make backup copies to start each computer, not to share copies. Both games are older so should be able to be found cheap somewhere.
Have fun!!
