There are all too many complaints about various Acer laptops that mirror what Gilbert G. has stated. My 5251 is in exactly the same boat. I have tried all the things Gilbert tried, w/o luck. Have swapped hard drive out; still no-go. Tested CMOS battery (it is soldered in), but it reads over 3 volts. so should be good. Have had laptop all apart and reseated all connections I could get at. Have swapped out the CPU, but that made no difference. I have come to believe that, somehow, the BIOS has become corrupted. The various “instructions” from diff. sources are not very clear about how one might go about reinstalling/reflashing the BIOS. I am trying various BIOS downloads, with a pressing of Fn-Esc keys; no fix yet, but the laptop does run the fan at full speed on some of the tries, so I am hopeful I will yet find the right “combinations” to make this work. Disappointed in Acer that they do not provide clear instructions on how to deal with BIOS issues.

Why not mention a bad CMOS battery? Numerous folks have stated this cause the laptop to not start up at all.