After upgrading to 4GB RAM, Poor performance on Windows Server 2003, Enterprise

[shocker]

The issue of Windows Server 2003, Enterprise not supporting 4G of
memory seems to be a common thread on this group. Well, I'm here to
add to it.

I've tried the /3G switch and the /PAE switch, but nothing seems to
help. My server runs faster on 2GB Ram than it does on 4GB.

I understand about the memory not being reported, so I don't care
about that. What I care about is the performance of the server. With
4GB installed (BIOS reporting Dual Channel memory config) my server
takes about 5 minutes to boot, and is very sluggish after logon. With
2GB (Dual Channel as well) or 3GB, it performs well and boots up in
just over 1 minute.

What gives? Have everyone given up on this issue? There doesn't seem
to be any real answeres to this problem.

Some details:
Motherboard: ASUS P4P800-X
4 HYNIX 1GB memory chip PC3200 400 MHZ
NIVIDIA Graphics