4 GB of RAM installed but only 2.97 GB usable. What gives? [duplicate]

Possible Duplicate:
Where did the other .8 GB of RAM go?

I just bought a used MacBook on eBay that came installed with 4 GB of RAM. The first thing I did was installing Windows 7 using Boot Camp. Here's where it gets weird. When I finally booted it up in Windows 7, I checked the Computer properties, and it said that there were 4 GB of RAM, but only 2.97 GB is usable. Why is that? Is there anything I can do about this?

Solution 1:

It sounds like you have installed a 32-bit version of Windows. 32-bit versions can only access around 3 GB of RAM. The exact amount depends on other hardware that is installed. If you want to be able to use more than this then you need to install a 64-bit OS.

Solution 2:

The long, detailed answer requires some reading. It's worthwhile though, see: The 3 GB-not-4 GB RAM problem.