typically it will allocate .5gigs (shows 3.5 gigs total a lot of the time) or so to video memory, but this isn't the issue you're having. It SHOULD show more than 2 gigs if everything is working properly. I'm not real sure what your issue is right now however. Its possible the new memory and you're board don't like eachother so I might would suggest attempting to update your bios for your motherboard and see if that helps things.
You are right, it is actually showing 2.93gig i.e. not including the amount assigned for video. However is there a way of viewing that and adjusting it? I mean if there is enough left unused could be turned into a RAMDISK