ap90033, I also have the E8400, DDR2 800 ram and have it at 4.0 stable. My settings:
Unlinked
FSB - 1779
RAM - 800
CPU core - 1.50v
CPU VVT - 1.35v
Nothbridge - 1.43v
LTD - 3x (Under Advanced Chipset Features)
Memory Timing - Auto
Would like to go higher than 4 but my abit FP-IN9 mobo...