I have a Dell Optiplex 170L with Windows XP Pro SP3 that is only seeing (and using based upon it's slowness) 508mb of the 2GB RAM installed. All 2GB show up in the BIOS, but when you boot into Windows it only shows 508mb in the system properties. So far I have updated the BIOS from AO7 to AO9, ran a CHKDSK /R, did a repair installation of XP Pro SP3, and I am currently doing a memory test using Ultimate Boot CD. I also went to crucial.com and had it scan the PC and Crucial shows that there is 2GB of RAM installed. I am perplexed. Have any of you experienced this? Thanks in advance for your help!