I have a Dell Inspiron AllInOne 3455 that does not seem to boot. I suspect EITHER a MB or screen problem. I can see the power button light come on and it turns white. I can hear the fan fine and the hard drive briefy but nothing ever shows at all on the screen. I replaced the HD with a known good bootable hard drive but same problem. How can I figure out what is causing the problem? thx.Display, Power Supply maybe, or RAM? Does it have HDMI or other way to connect it to another display to see if thats with nothing on it too?

When did this problem occur or did you get this system given to you this way?I am just looking at it for a friend. She said the system is a little over a year old and the problem just started. Its out of WARRANTY.
Does it seem like it would be the power supply when I can hear the fan still running until I power it off?
I thought of that but I was not sure it would recognize a second monitor if it was not already set up. Unfortunately I don't have any monitors with HDMI inputs and it does not have any other monitor connectors.Either way you need an HDMI monitor to diagnose any further...borrow 1 if need be...

BTW you cannot simply swap a Windows HDD from 1 PC to another and expect it to work...Thanks, I think you are right about borrowing a monitor. At least I may see some MESSAGE or not and that would tell me the monitor is the problem.
As far as switching hard drives it may not work completely but it will at least rule out the hard drive as the problem since you usually see some indication the system is trying to boot. I did not expect it to be a working system unless I was using its cloned hard drive. I really did not think it was the hard drive but wanted to try to rule out what was easiest first. Quote

As far as switching hard drives it may not work completely but it will at least rule out the hard drive as the problem since you usually see some indication the system is trying to boot. I did not expect it to be a working system unless I was using its cloned hard drive. I really did not think it was the hard drive but wanted to try to rule out what was easiest first.