I have recently changed my proc. XP 2000+ to an XP 3000+ (FSB 333 Mhz) on my KT3 Ultra2 equiped with 2 x 256 MB PC2700 memory. I Have upgraded my Bios to the last version to support XP 3000+ with 333Mhz FSB. In this configuration the system is stable, but if I add another 256 MB PC2700 I have a blue screen with the following error : PFN_LIST_CORRUPT "STOP 0x0000004E". This error message appear after windows has booted and I have opened a session. If I change FSB to 266 Mhz, It works fine with my 3 PC2700. My configuration is reduced to the mimimum : PSU : Seasonic SS-300 FS ( 28A @ 3.3V, 30A @ 5V, 15A @ 12V) Graphic card ( MSI Gforce 4) One disk (IBM) OS : XP Pro SP2 Any idea ?? Patrice