I have a Dell tower Model DHM and it has a BIOS pwd that no one in the office knows and is useless to us. I have removed the C-Mos battery (looks like a watch battery) to try to reset it, but can't find a jumper. Does anyone know how I can bypass this to reset it so I can use the PC?
I'm not quite sure which Dell model you have. "DHM" definitely isn't a model of the Dimension line of systems.
Removing the battery from the motherboard will clear the NVRAM/CMOS along with any forgotten BIOS passwords. Chances are when you tried, you didn't discharge the remaining electrical current on the motherboard. Until this residual charge is discharged, the BIOS will retain all its settings and passwords. Just do this.....
With the machine unplugged from the wall remove the battery from the motherboard. Then with the machine still unplugged press the On button for several seconds to dissipate any remaining electrical charge on the motherboard. Then re-install the battery, plug the machine back into the wall and boot the system back up.
Keep in mind by doing this method the time and date will need to be reset and all BIOS settings will be defaulted back to the way they were when the system shipped from the factory. Most Dell models have a jumper on the motherboard as you previously mentioned. Without knowing your model number it is difficult to point you to the proper documentation. The jumper method of resetting the passwords will do just that and won't default the other BIOS settings if that is a concern.
Ceri.... sorry if it seems I am duplicating your posting. I started typing my response and stopped midway through to let the dog out. After submitting I saw that you replied as well. Glad to see that you are now recommending the discharging of the motherboard by use of the On button instead of leaving the battery removed. It's a much quicker method.
Aaaah..... Optiplex, no wonder. Click here <ADMIN NOTE: Broken link has been removed from this post by Dell> for the on-line User Guide for the Optiplex GX260 and the section pertaining to the motherboard jumper for clearing passwords.
Glad to hear it worked and thanks for posting back with an update. In the future if you experience a BIOS related problem with your work computer there is a specific BIOS forum for the Optiplex product line. That forum can be found by clicking here. It's not that we don't enjoy answering your questions here, but since it is a business machine there are some slight differences from the Dimension line of home systems.