The .x files are the 3D models for the various ships, fighters, planets, etc. in the game. I don't know of any programs worth mentioning that can read in .x files, but there are a number of 3D modellers that produce .3ds files that can be converted to .x files with a converter (look for 3dsconv.exe); some of these modellers are
Anim8or and
Wings 3D (which is currently down

)
edit: oh yeah, the speeds of ships... in each ship definition in Main_PurchaseShipsPlayer.txt (or Main_PurchaseShipsEnemy.txt or Main_StartingPlayerShips.txt depending on which ships you want to modify) there should be an entry for the ship's max speed. This isn't the actual speed you'll get; you'll still need engines that can propel it that fast, though! To modify the engine components, go to Components.txt, remembering that the speeds in the text file are 1/1000 of those shown in the game, so to get a speed of 500, you'd put in 0.5 (like with the Ion Engine).
[ November 05, 2003, 16:40: Message edited by: Ed Kolis ]