@ srg86
I'm sorry to tell you that the OS is specifically the reason why I can't see all 4gb of my ram in Windows. Here is how I know:
1) On POST I have 4gb no problems.
2) On Windows XP32 SP2 when I have booted I see 3.25gb of RAM. It doesn't matter whether I use /PAE or /3gb boot.ini parameters, or change paging file parameters, that is what I am stuck with.
3) On exactly the same hardware setup, with a trial version of Windows XP64, I see 4gb on POST and ALSO IN WINDOWS.
This is an AMD 4200+ on a GA-K8N Pro Sli mobo but I am not using an SLi card. I know that hardware resources like PCI-E take up RAM, but not three quarters of a gb worth. Other users on PlanetAMD64 have confirmed my experience because when they have been in a similar situation and booted with only two sticks of 1gb each, they have not been left with only 1.25gb RAM visible in the OS. They have been left with around 1.75gb RAM, but the OS sees that he has 2gb of RAM.
I would love to be wrong about this, oh boy would I love it, but right now I can't fault my hardware setup for the RAM limitation.