OK the only way you can do it is to turn your FSB speed to 166MHz within BIOS, this will turn your DDR speed to 333MHz.
Oh by-the-way, just in case you didn't know and are worried; turning your memory speed down subsequently lowers your FSB anyway.
Is your memory clocked at DDR400? (PC3200)
Also there has been a lot of complaints about the Kingston ValueRAM - the RAM is unstable apparently.
[size=0.5]Full Aluminium ThermalTake Case
AMD Athlon XP 3200+ *400 FSB* Barton (2.2GHz)
ThermalTake Volcano 11+ Xaser Edition Air Cooling
1024MB Corsair TwinX XMS 3200 (Dual Channel 2x512) 2-3-2-6
256Mb XFX 7800 GS EXTREME
2x WD Raptors (10krpm 8MB Cache) 36.7GB using RAID -0
Video Logic SonicXplosion 5.1 Soundcard[/size]