Yes, they will work, giving you 768mb's of RAM. You won't have to configure anything. But in order for two DIMM's to run in Dual Channel, then they should be indentical (same size, same speed, same timings...).
But try it out, and see how it goes.
AMD X2 4400+ Toledo 1MB/Asus A8N-SLI Deluxe/2GB Kingston HyperX/SLI Gigabyte 7800 GTX 256MB/Creative SB Audigy 2 ZS Plat w/ Creative Inspire 6.1 speakers /180GB Hitachi PATA/19\" AG Neovo F-419 LCD/OCZ PowerStream 600W PSU/WinXP Home SP2