Normally 3 beeps means memory error in the base memory (1st 64K). Take out all the ram and reseat 1 stick then try to boot. If you still get error try the other stick that you added. Did you place a stick of 256 in one module? How much ram was the original stick? Can each module support 256 mb?
What fan are you unplugging? You def need fans being the cpu fan or a case fan you wouldn't want any overheating issues.