Windows 7: 4GB of ram But only 3.25 GB usable

I have windows 7 64bit edition a quad core processor, and 4 gb of ram. When I go to system in control panel it tells me that I have 4 gb of ram install but only 3.25 is usable, I looked this up on the internet and I found a forum that said Some memory could be allocated to the on-board graphics (which I don't use I have a graphics card) so I went into my bios but I could not find a single setting to turn off on-board graphics, then i read that you can turn on something called "memory remapping" but I couldnt find a setting for that in bios either. Is there anyway of fixing this?

I have An Abit I-G31 motherboard.

If you have not setup your BIOS to use the graphics card, you are probably still using the on-board graphics. And that can easily account for the missing MBs. But there must be a way to change your BIOS. I suggest you look again.
You should also have a look at the Resource Monitor > Memory tab. What does that show for "hardware reserved" - the grey area on the left of the colored bar.

It just says hardware reserved 770 mb's and there is no setting in my bios for disabling or enabling my on board graphics