Willing to boot an old computer with no BIOS support for USB boot and the only media you have is a flash thumb drive. If it happens and you face such problem take a look at PLoP.
You can install the boot loader in many different ways. My case: Windows were installed on the target PC. I installed bootloader using plpgenbtldr-0.7.zip according to its readme. Rebooted .... and ... computer is booting using USB flash.
