help with my motherboard

I have a KT4V motherboard made buy MSI and i was thinking of adding another 512 ram to my system. But here is where the problem is, I red in the motherboard manual that the motherboard only supports one ddr 400 dimm. Now is there a way to fix that with like motherboard updates. or could i buy a ddr 333 dimm and downclock my ddr 400 dimm. See i only have a athlon xp 2400 cpu so i don't think it really matters. I just want to add another 512 ram but i don't want to have to buy a gig of ddr 333 ram. Does anybody have any suggestions.

 

Have a look here. You should see if you have the latest bios or not. Also it says it will run on ddr333.