you might be able to play the PS2 version of NFL 2K5 on PC using pcsx2...I don't know how well it runs..but I wonder what other stuff someone can mod on it...its not originally a PC game, so i'm sure it would be limited...but I wouldn't be surprised if a programer was interested in it, he/she could do some stuff.
it turns out they just released their latest version..
http://pcsx2.net/