Quite honestly, the difference is 3.2mb/sec vs 6.4 mb/sec... Plus with only 256mb total, he is only using 64mb of video ram (XF86 config)... what does the bios say? The BIOS could be only allocating 32mb... Plus with more RAM the nforce 2 can allocate upto 128mb for vid ram...
Plus what speed ram is he using? PC 3200 or 2700? Or did his dealer install crappy PC 2100 or worse...
I think we need some more info... what Mobo are you using? How many sticks of RAM, etc?