passwords how to change password on the start up screen of a dell optiplex110?

Sounds like you are talking about a BIOS password. To access your BIOS you generally have to press delete during start up on the first screen where you see a memory test. If however you only see DELL splash screen then your best bet is contacting DELL and ask them. Also if you know what kind of motherboard you have and or the model number, you can do a search on the internet on how to reset the BIOS. Usually all you have to do is move a jumper on the motherboard then press the power button. It wont turn on when you do this so don't worry. Then switch the jumper back and turn on your PC and the password will be gone. Then you will be able to press delete to access the BIOS. In the BIOS you can set a new password or leave it without one. Also while you are there you will need to set the time and date. that is a must after resetting the BIOS.

Also you can do this by removing the battery and waiting several days. You have to wait because the capacitors on the board need to discharge. They do it on their own if the circuit is left open by removing the battery.

In my opinion moving the jumpers is quicker and easier.

Your BIOS has password, try removing the CMOS battery and let it sit for a day or two. If you have the manual look for jumper setting on mother board to reset BIOS password.

If all else fails, you may have to clear the BIOS password by resetting the RTC (Real Time Clock) IC (Integrated Circuit) on your motherboard.

I couldnt find an optiplex110 model listed on Dell.com. I did find an optiplex GX110 so I hope this is the right one for you. Please double check your model number before proceeding.

What you need to do is find the CMOS battery. It is a small silver battery similar to the style used in watches. If you remove this battery you will reset the BIOS to its factory default. You can view the product manuals provided for the optiplex GX110 at the link listed in sources. Simply choose the link for whatever size chassis you have.

reset the bios and reinstall an operating system