4GB Total memory using 2pc of  2GB PC2-3200 DDR2-400 Single-Rank Registered ECC DIMM.
Lifetime warranty for exchange. 
Brand Computer Memory Solutions
Features
Compatible with Dell PowerEdge 1800
MODULES MUST BE ORDERED AND INSTALLED IN PAIRS for Dual Channel mode.

First DIMM may be populated singularly, additional memory must be populated in pairs.

This chipset supports a maximum of 8 ranks.

If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation). Maximum configurations require a 64-bit operating system.