man , i learnt that u have p5-GC MX mobo and xfx 8400gs. I think ur mobo IGPU is consuming 128MB memory ( if u havent disabled it) and ur gfx card is consuming 512mb memory if m not wrong. (512+128=640mb). Appropriation means the memory is allocated to some device like ur graphics card or ur IGPU, since u have a graphics card with shared memory (8400gs = s stands for shared). u must have an option in ur mobo bios to control how much memory u want to allocate for ur graphics card. check it and see.

hope this helps...........

have u checked ur bios for gfx allocations as i said ??. just tell me if ur issue is sorted out....