For some reason, I opened it up tonight and started looking at the manual and stuff. Everything seemed alright until I looked at the disc. On the left side of the disc, it had this symbol:

Curious, I popped it into my computer, and a window came up asking to install! I did, and I'm now wondering: did I get a PC copy of the game in a PS2 case, or does this disc work on the PS2 as well? I'd try it myself, but I don't have the time at the moment to try to make this PAL game work on my NTSC PS2.
If anyone has any insight, it would be appreciated.