iso to bootable usb thumb drive

[crossbrand]

Ok I hope this is in the right place.

What I would like to do is take a .iso from a bootable cd\dvd and put the image on a usb thumb drive so I can boot from it in place of the cd\dvd.

I can do this with a a floppy but can't find a way to do it with a cd or dvd.

Any help would be great.