So I recently bought Splinter Cell: Conviction from an online store in Denmark that had it on sale. (I'm from Denmark FYI). 
 
Anyway, I  got the game and the case and disc says NTSC, but my PAL 360 can run it without any problems.. I have a Premium 360 20GB, bought about a year after it launched. I had it repaired and they replaced the motherboard and the DVD drive as far as I remember. 
 
So do you guys think this is just a misprinted case and DVD, or is my 360 magical? :o  

Curiously enough, I have recently noticed the same.  I have a used copy of the Orange Box, have long since stopped playing it, but only recently noticed that it is a NTSC copy. 
 
Either that, or we both got copies with wrong disc covers. For whatever reason.
 
Edit: Apparently, the 360's region-lock is game-specific. Weird.

I kinda want to play DP, so I was thinking of getting it and testing it out. Just a waste of money if I won't work :o

Yeah, it's game specific on the 360, some games will work others won't. You need to check it out before buying the game. I think DP is region locked. Not 100% though.

this same thing happened to me, i got a Assassins Creed 2 and it is a NTSC[J] and i played to on my PAL xbox, it works fine, then i bought NFS mostwanted which is also a NTSC[J] but it doesnt work, so just be warned that not all NTSC[J] games work on your pal xbox!

They're classed as Region Free games..