No, using another hard-drive for installation is not the cause for this problem.
Since most games today use DirextX 9.0 C, do you experience the same problem for other games?
Yeah, that's what I said, the MODELS of the WEAPONS are the SAME for BOTH games. Get it? No, well get with it.
And any mods? Or anything you tick-tacked (modded/tweaked poorly)?
I think the models for both games are all the same, the only difference is sound, damage, and recoil effects. Seriously man, those are yhe only difference.
Would you be a bit more specific?
Yup that should, but if you still have problems, be sure to have the most updated Windows Media Player, to either the 9th version or the 10th version with the complete codec package that comes with the official download from the official website of Microsoft.