The progams MAKE the file the same way on both your computers. What happens when you double click a file is a completely different ballgame!
First time you double click on a file with an unknown extension like .X, windows will ask you which program to open it in. Most people select notepad. You are also given option as to whether to ALWAYS open files with that extension in your chosen program.
In Win98, you can change that assignment by holding shift whilst right clicking file and you get new menu option called OPEN WITH.
Win XP always offers you a choice.
When you say computer compiles and renders the model when you doubleclick it. Which program is doing the rendering? Just change other computer to use same program.
The programmer formerly known as sonic