Aspire acer 5100-3959 notebook bios password

SOURCE: Bios Password Reset

The only idea I have is to find and disconnect the CMOS back-up battery after removing main battery and unplugging the AC adapter. That SHOULD clear the bios completely, wiping out the password, the date, and everything else.
I know this works on desktops, and most laptops, but no promises, and the cmos battery may not be easy to access.
You should probably leave the battery unhooked for at least 1-2 minutes to be sure it clears.

Hope this is some assistance!

SOURCE: how to reset password

To set the bio password, follow the following:

As soon as your laptop powers up, hold F2 until the ACER logo appears. Now press the right arrow on your keyboard twice to go to the: "MAIN" tab. Now press enter. You will be asked to enter the new password twice along with the original one. (if you previously had a password.). Now scroll down to where it says either: "Enabled" or "Disabled". If it is: "Disabled", press enter and select "Enabled". Exit the BIOS saving changes.

Done.

SOURCE: My Bios password has got reset

Hi Psyadav,
Try this link http://www.tech-faq.com/reset-bios-password.shtml , there are information on how to reset, with different way, a bios password.
Let me know if this article helps you.

SOURCE: Bios reset on a acer aspire 1640z

To reset the bios in a laptop you need to unplug the power supply and remove the battery. Once you do that press and hold the power button for 45 seconds then put the battery back on and plug it in and then try starting it. Everything in the bios will be reset to the factory. 
Good Luck

SOURCE: acer aspire 2920 bios password removing

The password to by-pass bios password are these, hope they will hope you, once you enter BIOS using these passwords you can reset it to normal
Phoenix Backdoor BIOS Passwords:

• BIOS
• CMOS
• phoenix
• PHOENIX