I have a laptop. This is the only system in my custody which runs on Windowz. Last few days I am observing a problem with it. It is not booting while I press the power button. Pressing the power button only light up Power LED but nothing shows in my monitor. If I remove the laptop battery and keep it open for about 2/3 mins., reinsert it and press the power button then the problem is going away and the machine is booting perfectly.

What is the problem? Thanks in advance.

Based on what you've said; it sounds like the battery is on it's way out.

How old is this machine?

Is the laptop overheating?

I agree, especially if the battery is several years old and the problem does not occur when the laptop is plugged into AC. If you have an electrical meter, I would suggest metering the battery to see whether it is charging fully to spec. If you don't have an electrical meter, you might consider getting an inexpensive one; they are handy to have around.

You might also thoroughly clean the contacts on the battery and in the battery bay with a bit of steel wool. There may be a bit of corrosion built up. Corrosion is not always visible.

Is the AC power still installed when you remove battery? (hope not)

If AC is removed along with battery then I assume that you have a quazi state where some part of the system has not fully powered down to a neutral state.

Have you tried booting your system without the battery plugged into your laptop?

I've only had one laptop that did not allow turning it on without a battery.

Removing your battery and letting it sit a while, is like any battery basically. If you remove AA batteries and let them set a bit, they tend to regenerate sometimes enough to get a little more use out of them before they are completely useless. That is probably why it will work whenever you pull your battery and let it sit. Nothing is pulling the charge out of it, ie the system clock. Even though it has its own battery, as far as I know that (CMOS) battery only gets used when no other power is present.

So if your laptop allows you to turn it on without a battery, (power cord plugged in of course. Redundant statement.) and it boots into Windows fine then a new battery is probably all you need.

I used to see behavior like that when a motherboard battery died and the clock would zero out (on desktops). It wouldn't boot because the data was newer than the current date? I assume old tech since you can remove the battery. You might look for a bios update for that hardware. Although it's probably just the battery, they don't really survive longer than 3 years in most cases, especially if you use the device on battery. Is it getting to a bootloader? Or not even to the bios info graphic (press ??? to setup). I would assume the latter.