I'd have to say Asus P4B266-E, if you can't find it go for 845 Ultra ARU, but I'd suggest going Abit TH7II-RAID. At this moment, Samsung PC800 that will most likely hit PC1066 speeds, is at most $10-15 more than Crucial PC2100 (some places more like >$5 more), and a 533fsb+PC1066 setup will outperform any overclocked DDR setup.