im putting in more RAM DDR. My current ram is 333mhz.

Will my comp still work if the RAM i buy is 400mhz or 266mhz etc? or does each stick have to be the same speed?

depends on what the motherboard handles, you can have different speed sticks, but they will all run at the slowest rams speed

could run s***

i got a 1800xp with an epox mobo here, and i just stuck in:

2x256mb kingmax ddr333
1x512mb corsair ddr400

and it ran s***fullness (previously running only with the kingmax)