Plop Boot Manager

There is tool Plop Boot Manager allows you to boot from USB disk even if your computer BIOS doesn’t support.

Firstly, download Plop Boot Manager and burn image into CD/DVD disk. And after that boot from respective device and you will this screen as shown in left.
On booting via Plop Boot Manager, you will see its own menu which lets you choose the device from which you want to boot. And this list includes USB booting as well. Thus, using this method you can boot from a USB device irrespective of whether your computer’s BIOS supports it or not.

Plop Boot Manager comes with USB drivers built-in and it can be used to access USB device of size up to 2TB, even if the BIOS supports only 128MB.