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Do you get any error message ?
for eg: Insert boot media in selected boot device and press a key
Let me clarify,
Do you get a prompt to enter BIOS password ?
What is the make and model of your computer ?
Please follow the steps below:Remove the AC power supply, then the laptop battery and finally remove the hard-drive and the watch type battery under the hard-drive. Then wait for about 10 minutes.
Then replace back the watch type battery and the hard-drive(screw the cover for the hard-drive back in place afterwards). Then just plug in the AC adapter(don't insert the battery) and power the machine on for a minute or so. You should see an error message advising the bios has recovered. Now you can put the battery back on.
Please let me know if you're not comfortable removing the Hard drive.