I have a HP ProBook 4310s. I'm trying to reset the BIOS on it. When I took apart the laptop, I found that it doesn't have a CMOS battery to help me reset the password.

Does anyone know how else I can reset the BIOS password?

  • I have Unlocked my BIOS on HP ProBook 4530s & answered a similar question <a href="superuser.com/questions/1108228/reset-bios-on-hp-probook-4530s" >HERE</a> by details. superuser.com/questions/1108228/reset-bios-on-hp-probook-4530s . This answer may apply for 4330s & 4570s ProBooks too due to same BIOS chip. Check it yourself. I hope it helps you too.
    – Omid PD
    Aug 3, 2016 at 12:09

2 Answers 2


Fiddling with the CMOS battery won't affect the BIOS password anyway. The BIOS password on that model is stored in an EEPROM chip which doesn't require electricity to store it. It was an improvement in laptop security that has been implemented by just about every laptop manufacturer. Being able to clear a password by removing a battery would essentially defeat the purpose of having BIOS security on a laptop.

No, the argument that this is how it works on a desktop doesn't apply here. I know there are a ton of links out there that all say just pull the battery, but these don't apply to laptops.

If the laptop does boot, but you just can't get into the BIOS, then you can try using the Kill CMOS utility or CMOSPasswd from Hiren's BootCD otherwise, you'd probably have to locate the EEPROM chip that the password is stored in, and short the proper pins while applying power to the unit to clear the chip.

Understandably, finding information on the internet pertaining to defeating laptop BIOS security is difficult... as it would make stealing laptops more profitable. I'll keep digging to see if there is a specific hack for that model.

EDIT Ok. I spent some time digging through the HP support forums, and multiple sources confirm that HP would need to remove that password. That means there are a couple of possibilities.

  1. If you enter the wrong password three times, you are presented with a unique code. This code can be deciphered and access can be gained. Not every HP professional series laptop comes with this system, but if your model does this, then visit Out-of-Warranty.com, register for free, and send them that code. They may be able to get you into the BIOS.
  2. The EEPROM chip has to be accessed and/or cleared manually. This requires knowing where the chip is as well as which pins to short. If this is the case, then it makes even MORE sense why the laptop should be sent to HP to have it cleared.

There is software out there that may or may not work, if you can boot the laptop to a CD or into Windows. Not all of it is free. Before you spend any money on any of this software, try the Hiren's BootCD option I linked you to above... but if no other option AND you don't want to pay HP for out-of-warranty service, you can try BiosPasswordRecovery as a last resort. Again... I just would not buy that software unless you have exhausted every possibility.

Now... I've gone as far as to make one of these tools here for hacking into an IBM Thinkpad to retrieve the BIOS password. It's a cute little cable that hangs on my wall now, and I need to keep a WinXP Home machine handy (since the software that works with the cable won't work with WinXP Pro, Vista, or Win7). I've done the procedure that is mentioned at the bottom of this page as well on multiple Dell laptops to clear the Eeprom chip. So, it's not all about being cruel or mean by telling you there isn't an easy way to do this. There doesn't HAVE to be an easy way to do this, because there isn't supposed to be an easy way to do this.

Oh, and your laptop either has a CMOS battery that you didn't find, or it was removed by someone else and never put back. With laptops, it's not always a coin cell battery. Here is a link to your service manual. Section 4 page 54 refers to the RTC battery, or Real-Time-Clock battery... otherwise known as the CMOS. In your case it is a coin-cell battery, within a plastic wrapper, attached to the motherboard by black and red leads.


There seems to be a software utility that works on some models of HP Probook/Elitebook to reset BIOS Password.

See https://forums.mydigitallife.net/threads/hp-probook-elitebook-bios-password-reset-utility.49497/ for more detail. HP ProBook 4310s is one of the supported models.

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