Ram Memory typically operates at half of the frequency rate, ('Speed'), that the Processor's -> FSB does.
Your motherboard supports Processors that have either a 400MegaHertz Front Side Bus, (400MHz FSB), or 533MHz FSB, or 800MHz FSB.
(Northwood Core for 400MHz FSB. The rest is in the other solution I provided)
Processor has a 400MHz FSB?
You can use DDR Sdram ram memory that is 266MHz.
Processor has a 533MHz FSB?
You can use DDR Sdram ram memory that is either 266MHz, Or 333MHz.
(PC2100 and PC2700 respectively)
Processor has an 800MHz FSB?
You can use DDR Sdram that is either 266MHz, or 333Mhz, or 400Mhz.
(PC2100, PC2700, and PC3200, respectively)
When using a processor that has an 800MHz FSB, and using PC2700, (DDR at 333MHz), the PC2700 ram memory will run at ->
JEDEC has set the voltage requirements for DDR Sdram at 2.5 Volts.
'Performance' ram memory that is DDR Sdram may use higher voltages.
Not recommended unless you know how to overclock.
Although the motherboard, and the ram memory module may have SPD, it doesn't always work,http://en.wikipedia.org/wiki/Serial_presence_detect
A lot of times you are faced with going into BIOS Setup, and changing the ram memory voltage, IF BIOS Setup has this feature.
This is why I say overclocking experience helps tremendously.
You want Low Density, Unbuffered, Non-ECC, and a CL of 2.5 for PC2700, and a CL of 3.0, (3) for PC3200.
[Why would anyone want to run PC2100> Lol! ]
For additional questions please post in a Comment.