I purchased a 255 mb SDRAM PC100 memory chip last week at Best Buy. I will work with PC100 or PC 133 bus systems. The older p/c I put it in will not accept a 256 mb memory card. Like an idiot, I sent the bar code to PNY for a $10 rebate, and cannot return it. I would sell the new memory for $50 shipped, or trade for a 64mb card and $25. I am not really conversant on prices and am willing to take the loss.