MBR rootkits are easy to repair. However, when it comes to bios malware and other hardware based malware, Umbra is right to say that it is near impossible to remove these malware.
In fact, if you are targeted by such an advanced threat, the recommended course of action would be to destroy the infected machine. That is because if the malware has taken control of the bios, it will be started whenever you boot up the computer, hence even if you use live CDs etc. to reflash your bios, the malware can simply trick you into thinking that the bios has been flashed while it is not. The way to go would be to remove the bios from your computer, flash it with another clean PC, and load it back into the computer. However, this is not possible most of the time as the bios is usually soldered in.
In fact, if you are targeted by such an advanced threat, the recommended course of action would be to destroy the infected machine. That is because if the malware has taken control of the bios, it will be started whenever you boot up the computer, hence even if you use live CDs etc. to reflash your bios, the malware can simply trick you into thinking that the bios has been flashed while it is not. The way to go would be to remove the bios from your computer, flash it with another clean PC, and load it back into the computer. However, this is not possible most of the time as the bios is usually soldered in.