OK, well I tried to upgrade the RAM in a friends macbook. It's a 1.83 CD with a superdrive, had 512mb, and I tried to upgrade to 1GB, which was the stock RAM from a C2D black Macbook. This is the 3rd Macbook I've upgraded the RAM in, and I did it just as I have the others. Except on this one, when I put in the 1GB and turned it on, the disk would start and the drive would check for a disc, and the screen would flash, and the white indicator light would flash repeatedly. So I tried the shut down and restart, reset the PMU and the PRAM and got nothing. So I put the stock RAM back in, and now it does the same thing, only the indicator light stays solid, and doesn't flash or anything. Anybody got any ideas??