I want to kind of recap this for readers, as the info has gone in a few different direction.
MB - Asus P5WD2 / Pentium D 351
RAM - Patriot EP 1GB DDR2 SDRAM (4GB Total)
OS - Windows XP Pro Enterprise SP3
BIOS sees 4GB
Windows shows 2GB
MAXMEM is unchecked and blank, but when checked only goes up to 2GB.
Is there anything else in Windows that might be set so it's limiting my RAM.
NOTE: When I 1st built the system I only had 2GB or RAM installed. Later I ordered and installed 2GB more of the exact same RAM.