Iphone

Dell PowerEdge 4600
Xeon 2.4 Ghz
Windows Server 2003 and Exchange 2003
Standalone Server performing all roles: AD, DC, DHCP, DNS, FS, Exchange, AS, etc..

Upgraded from 1GB of ram to 6GB of ram
Have 4 x 1GB and 4 x 512MB

Problem is in windows reporting it.

My Computer -> Properties shows 3.68 GB
Task Manager -> Performance shows 3,865,992

Yet Dell OpenManage shows installed 6144 MB
Total Installed Capacity: 6144
Total Installed Capacity Available to the OS: 5824

I have also recently setup the /3GB switch in the boot.ini (and the accompanying settings as per Microsofts memory optimize KB).

Questions:
Why is it showing different?
Is the OS taking advantage of the 6GB?
Any input?

I'm having some system problems that I might post in a seperate question if I can gather enough clues later. Honestly can't remember if the problems started before or after the memory install, thinking before memory upgrade ... around the same time.

Iphone

I'm assuming you are running 32bit windows 2003. As of any other 32bit OS, w2003 supports up to 2^32=4GB flat address space.
To use more than 4GB, your CPU must support PAE and you have to use /pae parameter for your windows os.

Large memory support is available in Windows Server 2003 and in Windows 2000

It's normal to see OS reports less than 4GB as it deduct space that is occupied BIOS.

Windows Vista or Windows Server 2003 may report less memory than you expect