my imac early 2008,after a hard drive replacement attempt which failed a holding alt/options never seemed to allow me to select boot options, suddenly started turning off after reaching halfway on the progress bar while booting. After my hard drive replacement attempt it did boot up fine a every thing seemed fine but every time i booted it up after it seemed to get slower with every boot and before it stopped booting alltogether it would take 20 minuted just to open chrome and even longer to get to a webpage. i heard that it was a temperature issue but i replaced the temperature sensor and even soldered a 1k ohm resistor to trick the imac into thinking the temp was normal but nothing worked. any form of commands while booting (reset pram, vram, recovery mode, target mode) doesnt work. some extra info : the reason the hard drive had to be replaced was because there were two partitions one 80 and one 270 which could not be resized or partitioned however i did manage to delete the 270 one with no data on it but the 80gb one with the mac os on it was still there and couldnt be resized despite there being 270gb free, also the imac was capable of going to select boot drive but recovery mode never worked and upon selecting the the recover partition in boot mode a Prohibition symbol would appear. Please help i need a solution fast and thanks in advance.