I'll explain it simple:

1. I'm planning to buy 360 while waiting for PS3 & Wii.
2. I like some games from the old XBox eg. the Halo series.
3. I did read some stuff about 360's backward compatibility. Most of old XBox's games can be played on 360, BUT, there are some software that needs to be installed and there are some issues to play them & during gameplay.
4. I have no lengthy experience on how XBox works inside out. Basically my experience is that I just turn ON the console & bam, I started fragging.

I hope someone who knows, better yet who has 360 & did tried them with the old games, can gimme some pointers (how the software are installed, what are those software, recommended software, issues of international old Xbox games being played on Japan version of 360, etc etc etc - something like that).
Thanks