Note book dell5100

You either have a problem with your power supply board or main board. I would start with having the power supply fuse checked as well as the power supply board!

starter

check if the cpu fan its working fine, maybe is damaged o dirty, you clean up with an air compress can

if still doesnt works you can try to replace the fan and see if it works

I would check any fuses first. The power transformer could also be open.There is a stanby supply that provides 5 volts that is always on . This is what supplys voltage for the standby light and the cpu. When you press the power button the cpu trips the power on relay that provides the 120v ac to the main transformer. If the transformer is open nothing happens. Onkyp part # is 2301798. Check the windings for continuity.

Check you bios configuration with Date and time correction.
See if your computer need cpu fan cleaning. Try to run F8 and scan your computer after you have accessed to safemode. Goodluck
JMC