So after switching out the original RAM, and replacing the original battery, my macbook booted perfectly, and everything seemed normal. Battery charged, RAM was registered and nothing else bothered me. Now, two days later, it's a whole different story. The machine is having trouble booting up. It gets almost through the apple logo loading screen, with fans running at full speed all the way, before shutting down, and restarting the process. I can, however boot it up in safemode (fans still running at full throttle). I can't seem to boot to disk utility, and I've tried resetting PRAM and SMC. Not sure if I actually did reset the SMC, but I followed instructions. Also, to boot it at all, I am holding the power button down for 10 seconds, then I'm plugging in my power chord. It won't boot with just a normal click of the power button. I also tried booting from a OS installer USB-stick, but same story with that one. This is soo frustrating, as I cannot tell what the problem is. Could it be the battery malfunctioning? I also tried putting the old RAM sticks back in, to no avail When booting to safemode it says 'no battery available' and 'low battery, your mac will sleep soon unless plugged into a power outlet' . (I am plugged in) Seems to me it's the battery, but any other ideas? And what's up with the fans?