Memory, 4GB, and 32-bit

Since my little experiment with i-RAM was big flop, I was considering removing some or all of four DDR400 1GB modules from i-RAM and upgrading the memory for the main system. I didn't find many use for 4GB storage but I could use 4GB of main memory since the running even two guest OS in VMware was virtually impossible for my 1GB memory (currently running four OS in four different machines). I can install pretty much only one Linux distribution on i-RAM but I can install and run multiple Linux distributions using VMware. I am aware of the problem that my Athlon64 3500+ (Winchester core) has little problem supporting four memory at 400MHz; if four memory sticks are installed, the memory speed will drop to DDR333 from DDR400. I believe it was corrected since Venice core. However DDR333 wasn't bother too much but I really want to run multiple OS at same time.

I was looking for a excuse to upgrade to 4GB RAM. And I found an interesting article on slashdot. It says:

On Vista, 4GB of RAM may be closer to its "Nirvana," ... That's due in part to Windows SuperFetch, which takes data from the hard drive, stores it in the available RAM and makes it readily accessible to the processor.

It sounds a lot like what Firefox did which people called as memory leak. Nevertheless it was good news to upgrade to 4GB RAM until I found about 4GB memory support from 32-bit Windows Vista and Windows server 2003. Since early day in my computer science class, I've been told that the most of 32-bit OS and processor support addressing of 2³²=4294967296 bytes of memory. The only road block was the availability of large memory stick and motherboard. Since my motherboard supports up to 4GB, I was surprised to hear this:

On a computer that has 4 gigabytes (GB) of random access memory (RAM), the System Properties dialog box and the System Information dialog box may report less memory than you expect.

from the Microsoft Knowedge Base article. Later I found that, in 32-bit system, the old and outdated BIOS in our PC reserves a part of memory for devices; resulting not all 4GB memory was accessible. There are more articles about this issues including one from MAC. Now I'm not sure I should go throw the hassle of removing computer case to upgrade my memory to 2GB and downgrade to 2GB i-RAM.