Sorry Drunk , my French ain't up to much :-(
I take it that a "ordinateur" is a "laptop" ?
If so , first id say that XP won't break under normall circumstances , works fine for me on both laptop and desktop.
However if you don't want it , then you don't want it :-)
Simply boot off the 2000 CD and follow the on screen prompts , your laptop will need to be set to boot off a CD , normally is , you will be then confronted by a 2000 install menu , follow that .
Select format during the install , and continue.
You may encounter some problems , first one is 2000 may tell ya that there is a newer OS isntalled and quit , you would need to boot from a boot disk, and wipe the drive first .
Second 2000 may not see all your hardware and will need to find drivers for some if it .
Personally i would not suggest you "downgrade" to 2000, it may well not run properly as the hardware is newer than the OS.
As a generall rule you should run the OS that the machine was built for , in this case XP.
You could upgrade to XP pro, it's better than XP home.
I'd run it for a while and see what issues happen along the way , rather than installing 2000 .