I only have a paltry 512MB of RAM for my 15" PowerBook 1.5GHz G4. Since having multiple applications open at once makes things excruciatingly slow, I am interested in installing some more RAM. Where can I find good, inexpensive RAM? I know that Apple RAM is way too expensive. I’ve heard good things about Crucial. Also, what would be the difference between getting 1GB and 512MB? How much faster would the additional 1GB be compared to the 512MB? Since I have 512MB already, can I only put another 512MB in? Finally, any general tips when installing your own RAM? Thanks for the help!