Do you have to make a bios backup in order to install an OS like windows xp?
No, to my knowledge the BIOS of a computer is not affected by
the installation of any Operating System (OS). The BIOS provides
some common information to the OS, so the OS does not have to know
specific things that may be different from computer to computer,
like the type of hard drive for example. The BIOS takes care of how
the hard drive is configured so the OS does not need to worry about
it.