I have a 15-inch 2.0 Ghz MBP that originally had 512 Mb of Ram. I just upgraded to two Gb but when I went to confirm that that new memory was in by checking in the Activity Monitor, the program would not open. I also tried to connect my external hard drive but its icon never appeared on the desktop. When I removed the external hard drive, I did NOT receive a message telling me that I had ejected it incorrectly which was something that I also found interesting. The new memory sticks are: mushkin 1GB DDR2 667 (PC2 5300) Model 971504A. The external is a Western Digital 500 Gb that I have never had any problems with. What have I done? Someone help me. Thanks.