I agree with ElDiablo about the RAM. Also, if the laptop can handle just about any OSX package (including Panther), then it can handle Tiger. Some of the effects like Dashboard zooming in and out will be a little laggy, but overall it will be quick and useable. I have a friend that has a 400MHZ PowerBook w/ 256 RAM and Tiger runs fine. In fact, he says it's much much faster than Panther.