I'm trying to find out which place has the best 512mb RAM price for my 15" PB (1GHZ model). Quick question: The 256mb on the PB isn't soldered on, is it? If not, there won't be a problem pairing it up with different size RAM, correct? If so, I'll have to save up for two pieces of 512mb RAM. Any help would be greatly appreciated. Thanks a lot!