Multiboot Install Hard Drive

[maccam94]

I'm looking to make a multiboot drive that will be able to be plugged in via USB (IDE if this is not possible). It is going to include lots of drivers and some useful security tools, as well as some configuration options, but it will also contain both XP Pro and Home. I want to make it possible for this cd to accept either retail or OEM keys for both OSes, because this will be used in a computer repair shop where cd keys are often available but not the cds. I know that there is a file that controls which keys the disk will accept (i386/setupp.ini), and here comes my question:

Is it possible to write over the setupp.ini file based on user input? For instance, if I choose to install XP Pro, OEM, via the menu screen, can I then have the bootloader either write a certain string to the setupp.ini file or overwrite it with another copy somewhere else, so that it will accept the proper key?

Thanks in advance for the help!