Did you follow the instructions on how to make the usb stick a bootable device? If you did then the computer should see it as just another hard drive and you will be able to boot from it.
Hi Inzone, older PCs do not have the support to boot from a USB drive. Most (all?) newer PCs can. IDE drives and SAS drives and SATA drives do not really look the same to the BIOS, the operating system makes them seem the same to the user.