Then I found that I could write my iso files in a usb flash drive and boot from that key. While most of new pc models were capable of booting off a usb drive, some old pc models (on which I usually test ultra-lightweight Linux distrubutions such as "Puppy Linux") cannot boot from usb keys.
However, there is a way to bypass this awful motherboard restriction and boot from usb flash drives without modding the B.I.O.S.(!!!!do not try this method unless you really know what you are doing!!!!).
In this instructable, will bypass this restriction using a linux based bootmanager. This bootmanager can be written on a disk or on a floppy disk.
Step 1: Things you will need
---------->iso burning software (cd burner xp,magic iso......)