According to what am getting, is that you have set your machine to request power-on password and you have forgotten the password,OK. If that is so, I'll give you a solution based to that question and i have also tried. You should try this when your machine is OFF.Shut it down.
I don't know if you are well versed with hardware part of the computer, if so do the follwoing (if not find somebody who know computer hardware and let him/her solve this problem for you.)
Open your computer CPU, if it is a desktop computer.(In-case of a laptop, it's not that easy but impossible is nothing.) Try to locate where the CMOS Battery is, this battery looks like a 'Big' watch battery. The work of these battery is to keep track or memory to your computer about Time and BIOS Settings.
After getting the battery, please carefully remove it. Remove the power cable from your machine for at-least five minutes to drain all the power. Then power on the machine without the battery, you'll notice it won't ask you for the power-on password. Then shut-it down and again carefully insert the CMOS Battery.
Power-on the machine and you will be requested to Set date/time (Please do this in the BIOS), then you can decide again to set the power-on password or not.