http://support.asus.com/faq/faq.aspx?SLanguage=en-us
http://forums.hexus.net/showthread.php?t=89233
asus p5b mobo has problems... When you first boot the system does it see the correct number of ram .. try removing the ram and only putting 1 socket.. you could have 1 bad stck of ram ... try each stick on its own.. I have had the problem b4 on other boards and thought the system was FuQ'd and it was just same bad ram.