A7v8x-x

take your time, still waiting for an answer.. lol

Not sure about the RAM issue, but the aperature is how much RAM the GPU uses if it runs out of memory onboard. For a 128MB card, I would leave it at 64 or 128.

If that mobo has 3 bancs of memory it is supposed that they are usable. I don't see why asus would put on a mobo three bancks of ran if only one of them is able to be used.
If you can't put your ram to 400 it can be one of the folowing: the ram is actualy DDR333 (wich I doubt) or the bios simply doesn't let you to put the ram faster than the CPU fsb. Your cpu has 333 fsb I suppose, and setting a different asyncronious freq for the ram would make the performance of your rig decrease evan thow you raised the DDR to 400. On the XPs those things, the fsb and the ram speed is better to be sync.
You can always try a bios update, maybe it's a bug.
Cheers!

hold on, me thinks your getting confused with banks and slots, I have three ram slots but i can only have 2 banks of PC3200 or 4 banks of PC2700, i.e. one bank equals one sided ram, 2 banks equals double sided ram.