Although this may sound a little weird, if a laptop appears to turn on but does not actually load the OS, it is (possibly) due to the unit having gotten into a “stuck power mode”. The reason(s) for this are complex but if this is happening to you, there is an easy procedure to try called a “Hard Reset” and it really is fairly simple:
1. First ensure that the unit is powered OFF.
2. Next be sure to remove the AC power input cable.
3. Then flip the laptop over and REMOVE the BATTERY. (Consult manufacturer’s instructions or post here)
4. Once all power is removed as stated above, place the laptop normally on a flat surface then PRESS and HOLD the power button for 30 seconds.
5. Now replace the battery, plug in the AC power and turn the unit on as usual.
If the reset worked the laptop will now boot normally. If the failure remains then the unit will require more troubleshooting but it would be a lucky thing if it were only the hard drive or the power input module that was at fault because often (depending on model and age of laptop) the motherboard is at fault.
I have done this with many laptops over recent years and it does work in many instances. From the average perspective this would likely seem to be a shot in the dark but the fact is simply that it can work.