Put a gig of PC3200 in one and a half gig of PC 3200 in the other.
The extra wiring length from the third slot may make the memory timing marginal [flaky]. The last thing that you would want is flaky memory performance.
I'm building a new machine around the ASUS K8V mobo and Athlon 64 3000+. I'd like to install three 512MB,DDR 400,modules in order to get 1.5 Gigs of memory. The Asus manual, however doesn't list that combination on their "recommended configuration" page. They only recommend filling all 3 slots when using DDR 333 or slower. My question is: what would be the ramifications (no pun intended!) of using 3 of the DDR 400s? And, is there a significant difference between the 333 and 400s, operationally? At 70 years of age, I'm not into heavy gaming, so don't need cutting edge. But I do want to build a fast, powerful system that will allow me plenty of room for future upgrades. Thanks for your input.