Why is Grand Theft Auto IV for PC reading only 250mb of graphic memory?

I have installed Grand Theft Auto on my computer, and started playing it but the graphics are pretty bad. When I try changing them in the game it won't let me put the quality on high until everything is set at 0. On the bottom it says my graphics are near or have exceeded the suggested resource limits for my system. It says I only have 250mb but I actually have about 2gb of graphic memory. Any way to fix that?Why is Grand Theft Auto IV for PC reading only 250mb of graphic memory?
Are u sure that u have 2gb VRAM??This sounds....futuristic.Probably ur VRAM is shared,that means u dont have 2 gb but 256 mb(or 512mb)and the graphic card steals the rest of the memory from the RAM.Anyway,actually u can configure exactly how many VRAM u want to use,restart ur computer,press f2(or f8 or another F key,its different key in each pc manufactor) and get into the BIOS.Find the graphics settings and then u can choose the amount of the VRAM u want to use.If u choose more memory than ur actual own VRAM,then ur RAM is getting smaller(for example if ur actual VRAM is 256mb and u choose to have 512 mb VRAM,then ur graphic card steals 256mb from the RAM and ur RAM is now smaller).Save ur settings and restart ur computer.