hi, let me tell the story from the beginning, I have 2 batteries one is working and the other one is dead, i use the dead one when i want to connect the power for let say a whole day, so my working one wont get exhausted. so what happen after leaving the dead one for almost one day, i came to my MBP and took off the power wire forgetting that its the dead one, so as you expect the MBP shutdown. now i changed the battery to the working one and turning it on, everything went fine however it got stuck at the start apple sign with the thing spinning. so i tried to restart more than one with no use. so i did the following to solve the problem all didnt help: 1- I rest the memory of some sort. I pressed (option+command+p+r) while starting MBP 2- Resetting SMC 3- Testing the hardware, Pressing D while starting the MBP , the apple hardware test show up, did the test which checked the memory and logic board and hard drive with no problem at all. 4- I pressed the option key to choice different start up disk, it let me choice it, but when starting it stuck the same place .( tried from external HD with Leopard) 5- tried to press C while starting to boot from leopard dvd, didnt work. 6- tried starting with shift key for safe mode didnt work at all. now my last option which isnt appealing is to take it to apple store, which where i live they dont have genius bar, they just send it to specialized place some where which will take some time. my MBP is 2.8 late 2008 i think. I have notice many here are well experienced and could solve my problem thanks.