There are a number of methods to remove bios passwords from systems, some can be removed by simply reseting the cmos by flipping a jumper, some can be removed by removing the bios battery. However other systems adapt a higher level of security and the only way to remove the bios password from those systems is to either short circuit the cmos eprom chip on the motherboard, or using a dedicated pcb programed to access the cmos chip where the password is saved. This device will access the information from the cmos eprom chip and you can then clear this information and then save it to the chip.
Some manufacturers like Dell provide a code which you can then enter into an algorithm which is freely available online using the links below. The site will generate a master key which will allow access to the bios. From there you can then remove the password and your bios is password clear once more.
Recently I cleared the bios password from some Acer Veriton computers, it was a simple process once you have located the cmos jumper on the motherboard. Please check out the video below for details.