Hi, I have a very strange problem with my HP ProBook 4540s so ANY help is appreciated: Press the Power button, the power LED turns on for like 1.5 seconds (including the caps lock, AC LED and also fan, the display doesn't turn on) and then turn off and then he tries to startup again and sometimes it does show the HP screen and boots normally sometimes doesn't and turns off and then on for 1.5 seconds and so on and on... I tried: - Reflash the latest version version of BIOS - Rollback of BIOS doesn't work (invalid signature file says when I try to flash the BIOS but I tried different versions but same problem) and I still have no solution for this to work. - Take out SSD. - Take out the RAM, I tried switching the slots but has no effects. - I tried reset the BIOS via taking out the CMOS battery. I even replaced the battery and nothing. The problem is present no matter if I am on battery or AC power. It happens randomly, sometimes it boots up on second try sometimes on first try sometimes at all. I hope that I explained the problem good enough, If you have questions please ask me because this problem is driving me nuts !!!