Normally I try pretty much EVERYTHING before going to forums for help, and in this case I can definitely say thats true. I've had this problem with my Macbook Pro 1,2 for about a YEAR now and have tried EVERYTHING I've read on every forum and all over the internet. A lot of people have had similar problems, but I'm hoping the odd and unique symptoms of mine will help someone figure out what could be wrong. As I recall the problem started when I tried to add an additional 1GB RAM into the top DIMM. It was PC2 DDR2-5300 ordered directly through crucial's "Scan my computer to determine the best RAM" type program. When I booted up after that one of two things happened;either the front LED flashed (yeah, a memory problem...) or it lit normally but I got a black screen. I removed the RAM and went back to my old config. Here's when the main problem started: Since this attempted upgrade when I try to boot up my mac my computer hangs at the gray screen with nothing on it (no mac logo, spinning wheel, etc.) At first it was usually a matter of time before it would finally boot (sometimes up to ten minutes) but here's EXACTLY what happens now. 1. I boot up, it hangs at grey screen and I hear a very light constant noise that sounds like the hard drive spinning (barely noticeable standard drive spinning up noise I hear when all my computers start.) 2. The noise stays constant or sometimes sounds like its starting to speed up as if it is trying to boot but then cuts off and goes back to the same constant quieter noise. 3. Here's the weird part. If i flip my Macbook up vertically, so the top of the screen is facing either forward or down, and then flip it back to normal sometimes the drive starts spinning louder and then boots up (Apple, spinning wheel, OS X.) If that does not work I give it a few taps on the underside, mostly near the battery, and THEN it pretty consistantly starts spinning louder and boots up. I have NO idea what this could be, I've tried every combination of startup keys, cleaned out the entire inside of the computer, and replaced the hard drive two days ago. In addition, I tightened up all the components and tried to install another 1GB PC2 DDR2-5300 667mhz RAM DIMM wth the same results. It also worth noting that the current RAM only works in the bottom DIMM, and will simply boot to black if in the top one. This curiously seems to be very specifically contained in booting up, because after I installed Vista via Boot Camp the other day I noticed a similar thing happens when I boot into Windows. After starting up, tapping away at the bottom, and then getting to "Option ->windows partition" I get a black screen with a constant "_" pulsing on the screen. I flip it over, tap it some, and it finally boots into Windows. Any help would be GREATLY appreciated, as I really don't want to wait another year to figure this out, thanks!