Over the past few weeks I've been getting intermittent BSOD crashes with "unexpected IRQ" or "page fault in non-page area" errors. These were often accompanied on reboot by POST beep code 1-3-4-3, error in first 512K of base memory. Memtest86 fails after a few passes with the unexpected IRQ error. Replaced both internal and external OEM memory modules (Hynix 512MB PC2700S DDR 333MHz) with two PNY 1GB PC2700 333MHz modules. Things are worse now. Getting POST beep codes of 1-4-1-1 and 3 and 2, all having to do with memory. Questions: 1) What is the significance of "S" in PC2700S? 2) Are the internal and external modules the only memory to worry about, or is there some other motherboard memory that could be causing this? 3) Suggestions? Thank you.