Yeah, that was the issue. I didn't know the key for sprinting, and forgot that you could even sprint in the game. Now to cross that ledge that leads to the red key, you need to sprint and I must of forgot that was how I crossed it way back in the original doom 2 as a kid.

Thanks.  I must of forgot back when I use to play the orignal dooms as a kid.  The only reason I thought it was possible becuase I guess the doom I have on my pc is modified to allow jumping, and moving of the cursor to look around. 

I''ve been a doom fan since the original doom, and I have owned all the other dooms including part 3 when they originally came out.  I think there is a big issue though with the original doom's. You cannot seem to be able to jump. On the 2nd level of doom 2, there is an area where you need to jump up a ledge to get the red key, you cannot jump in both xbox 360 version and PC version. Hopefully that'll get patched.