Rather then debate multi-threading, I just went to the source .. from microsoft's website:
You can vew the full deal hereMultithreading. Right now the most sophisticated games require computers to complete many different processes at once. This is known as multithreading and as games evolve multithreading will become more and more important. Windows XP handles multithreading more intelligently than previous operating systems. For now, any game that requires execution of multiple tasks within its own process will benefit from smoother graphics and some overall speed gains
Now in regards to "When you send a task in background it stops and wait to be relaunched" that's just bogus. I know several games that will run just fine in the background. Things change, time passes, resources are collected, all in the background (In fact Rise of Nations by Microsoft does just this). To say otherwise just shows a total and fundamental lack of understanding of the OS.
The fact is that X2 was either not written so that it can run in the background, or they purposely disabled the game while in background mode. It would take a developer to tell us which way. However, you are incorrect in many of your assumptions regarding background tasks. In fact, just to prove it to myself beyond a shadow of doubt I have Rise of Nations running in the background right now. Task manager states that it's using approx. 80% of my cpu. And ... let's alt-tab back into game ... I now have 250 more units of wood and since it's only being collected at 45 units per minute, I'd say it's running just fine in the background.
You are correct that services will run in the background, but that kind of goes w/o saying. What good is a service that doesn't run in the background? My entire production farm at work would be useless if the applications did not run in the background as services.
The point is Windows can handle multi-threading, multi-processing, and multi-tasking. The software has to be written to take that into account, and X2 was not. It's a "problem" with X2 and NOT the OS.
I put problem in quotes because I don't consider it to be an issue at all, it's how they coded it, deal with it
OH, and I just checked Rise of Nations again and I now have 450 more units of wood. Meanwhile, the computer has advanced to the next age, and has almost completely destroyed my town. All of this while it ran in the background as I typed this message to you. Feel bad for my village, but oh well, it was just a test anyway