The memory range you reference is only available to the kernel / system (The 4th GB). It can see it, though it is unlikely to ever use it. A 32-bit OS can't see beyond 4GB (Well, this is not true, but for XP / Vista it is).
Add the /3gb switch to your boot.ini profile. You can make apps built in Visual Studio 6 or later able to access a full 3GB instead of only 2GB.
This can break older apps however that crash upon seeing anything more than 2GB available - a just FYI thing here. The point being, you probably don't have any anymore apps this old.
-S
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