Just to let you guys know some things about HaloPC...
It runs just fine on my 800Mhz P3, 256 Megs of PC133 Ram, Ti4200 128 Meg card
The patch that was released was for the multiplayer online, it disabled the previous crack that allowed you to download the game and play online, but the Patch was hacked within 5 hours of official release so that is why when you play you may see some servers that say Cracked as you can only play on Cracked servers if you have the Cracked game...
But the game is pretty good... not too much of an improvement over the XBOX version, The new weapons are alright, Flamethrower is too powerful and the Fuel Rod Gun is too weak, Banshee is fun, but its even more fun to shoot them out of the sky with a tank...
If you liked Halo on XBox I would recommend trying this out, the MODs that are going to be coming out for it are probably going to be worth it