I Knnooww This Has Been Reported A Thousand Times, Butttttt..

Cauliflower - Raging Tide

Alright, so the deal is with my pants. They keep disappearing on certain angles. I know this is a very old problem, and there's been a lot of threads on this, but I've been searching all over, and not one thing I've tried has helped it. I'm also concerned if people can see me pants-less; because I've seen many people running around naked (well, with underwear). The threads I've seen usually ask for a "dxdiag" screenshot, and here's mine:
Pleeease help, it bugs me.