should work,as long as you have them running at the right speed. worth noting that ram with two different sticks at speeds will run at the slower ones speed,so if overlocking make sure of the slow speed. does the mobo run the current stick at 400mhz?
hang on, i just checked your board out and it supports 2gb at 400mhz, so another pc3200 stick should run fine. i had a board with the same chipset and 2x 512 pc3200 worked fine for me,different makes