In this order I do this.
1. Ask the owner about the Fn key their laptop uses to switch from internal to external display. NO I am not telling you this information. It's part test, part how I solved a few of these and the owner learns about their laptop along the way.
2. Next, the other reset. We remove the AC, the big battery then press, hold the power button for a full minute. Reassemble and try again. NO! This is not going to work for everyone. Sometimes people want to know ahead of time if this will fix it.
3. Finally we replace the cheapest possible part it could be. The internal RTC or CMOS battery. It's under 20 and sometimes 75 cents. Again NO to the question if this will fix it. These are free to cheap steps that work in some situations.
4. Now we have to decide what next. At this point we find a replacement motherboard.
One day my compaq presario F502 ea laptop went into hibernation and it hasn't been able to start up again. After I turn it on it makes the usual starting up noices and then restarts without displaying the usual startup messages on the screen. I have removed all my school work and important information from the hard drive by connecting it to my desktop as an external storage device. I scanned it afterwards to check for any errors on the disk and it was fine.
I have tried connecting the laptop to my desktop monitor but that didn't work either. I'm now at my wits end. Please, please, please somebody help me restart my laptop.