generally old bios doesn't support boot from usb, but with this "plop boot manager" u can boot from usb without any problem,


1-download plpbt plob boot manager:http://www.plop.at/en/bootmanager/download.html

2-copy the files "plpbt.bin" and "plpgenbtldr.exe" in c:\\

3-open the command promp and type the commands bellow
          cd \
          plpgenbtldr
          start boot.ini
4-in the last ligne of boot.ini file type:
c:\\plpbtldr.bin="pLop Boot Manager"
and save this file

5-reboot your computer
6- choose "plop boot manager" at the startup
7-choose boot from usb