I decided to give Apple/Mac a try after many yrs on PC's. Since I wasn't sure I'd like it, I got a used one. It ran fine for several weeks. I was liking it and decided to upgrade the RAM. I bought a 1gig and installed it. This ran fine for a few days then it started showing only the upper memory (256) and 1/2 of the lower (512) or 768 total. I removed the 1gig and reinserted it. On restart it again showed the full gig. Then on the next restart it went back to the 768. I just started using it this way and I a screen popped up telling me I needed to restart the computer. I did and it rebooted. Then a little while later the same screen came up. I restarted and this time it would not reboot. It gives the chime and comes to the Apple logo with the spinning wheel. The wheel spins and spins and spins but it won't go past this. I tried reinstalling the original 256 memory boards. This didn't change anything, still boots only to the logo screen and spinning wheel. Sure would appreciate some help with diag. or repair steps. Thanks in advance, bmwrider Anyone have some advice for me?