Booting from a USB drive on a PC that does not support it is challenging, primarily due to BIOS limitations. If the BIOS does not recognize USB booting, no software adjustments can enable it. One potential workaround involves booting from a CD and then transferring control to the USB drive, similar to older methods using floppy disks. Linux distributions, particularly lightweight options like Puppy Linux or Damn Small Linux (DSL), can be booted from USB, but if the BIOS lacks support, this won't work. Creating a bootable USB drive involves specific techniques, such as making the USB appear as a floppy or hard disk. However, the boot record's limited space restricts loading USB drivers directly. Some users suggest using live CDs to load USB drivers after initial booting. Knoppix is recommended as a user-friendly option that can run from both CD and USB, with DSL being a remaster of it. Ultimately, if the BIOS does not support USB booting, the options are severely limited.