hey im having some issues. i have 4gb of ddr3 1600 mhz (i would have but 1 stick of my trip channel doesnt work

) but my version of windows x64bit, build 1700 reads only using 1.99gb of the 4gb total memory.
i know it registers 4gb 'cos it all checks out in the bios. AND because it says total memory is 4gb. but when i go into task manager it only reads 2gb being used.
is this just windows 7 doing some wierd "im only gonna TELL you im using less ram" thing or is there a fix or an update to fix this.
thanks