XP Memory Managment

I am working with some very large TIFFS. They average about 1.2 GB each. I am unable to open them in any of my image editors. They require that I have at least 3 times the files size in free system memory. So here is the problem.

I went out and bought 4GB of DDR800 4x2GB and out those into my 4 slots. Of course 32 bit XP MCE only sees 3GB. My question is, how can I get windows to see a little bit more of that RAM. I only need another 600 or so MB and I'm in business.

My video card has 256MB and I have set virtual memory to 0, PAE is on, but still only 3gigs. I even tried some of the free managment utillities in the downloads section. Most seem to have been designed in the 98 days and manage to spot only 2 gigs when ran.

Thanks