So I've had my 4.1 for more than a year now, ran without issues the whole time (I'm the second owner). I haven't turned it on for two days or so and when I did this morning, my system couldn't boot up. I hear chime, my display switches on after a while and I only see white screen - there is no circular loading symbol, no apple logo, nothing. So I tried pulling off all drives. Same result. I tried pulling of all RAM - logically without any stick, I won't even hear chime (only blinking power button). Then I tried putting one stick in each slot (I have four 8GB sticks, regular DDR3), I did this with two sticks but it would always get stuck on the white screen. Sometimes red light on mobo flashed quickly after pressing power button, I think it happened when I put single stick in slot 2. I pulled out the original two gig sticks and tried two of those but still nothing happened. Of course I had only my display plugged in. Also the computer draws power from CyberPower UPS but that shouldn't be problem. I never had any issues and frankly I'm quite concerned it's mobo problem or something. The only "weird" thing this computer had was everytime the display would turn off - either from sleep or when booting, it would take like 5-7 seconds to display anything (I use it with regular DVI display), sometimes the colors were pink-ish for like second and then everything would go back to normal. I wish I had spare GPU to test with but I don't. Mine is ATI Radeon HD5870 (1 gig version). This computer had power supply exchanged in the past. Unfortunately this 4.1 ran out of warranty few months ago. When I try holding option (ALT) key when booting up, it does nothing. Any help would be appreciated. (Don't worry guys I have my backup of my important stuff). P.S.: I also noticed when I let my stuff plugged in - logitech webcam and Onyx audio interface, their LEDs were on. Sort of like stucked, normally they just light up and then stop. I also tried reseating CPU board. P.P.S.: I tried holding option-command-p-r for PRAM reset, it seems it responds to this command but unfortunately does nothing. P.P.P.S: If I leave the computer on nothing happens, only fans kick in after a while which is weird but probably related to this problem.