not sure if it's the right place to post (I'm kinda in a hurry and got to leave in a few minutes)

I succesfully installed the whole game, but whenever I try to run either SP or MP, it show me the intro screen, then it try to laod for a few seconds, and a windows error windows appear asking me if i want to try to debug, send an error report or not and that's it. I asked my friend, he said he had this problem too, and that he reinstalled the game. I did so, but it still show the same error window.

Any solution?

Sounds like a Windows error more than anything else. Go to here> http://jediknight2.filefront.com/file/Jedi_Knight_Academy_Patch_101;20459) and download the Lucasarts Patch.
Once it's installed it changes the structure of jamp.exe which should solve your problem.
It's worked for people in the past anyhow :)

B.