I always get confused about this. My machine has 4GB of RAM and is recognized during the Dell boot up process. Once in Windows Task Manager, under "Performance" only 2 GB is recognized. Somewhere I read that XP is only able to address up top 2 GB. There is a switch that you can set I believe its in the boot.ini file that can get it to recognize 3 GB.

I've never been successful getting this to work.. The 4 gb (I'm told) would be recognizable by the 64 bit version of the operating systems... but that seems like it might open more problems then its worth....