Install OSX from USB stick

I have a friends macbook that im trying to upgrade to Leopard. (not enough memory for Snow, Lion). Im trying to create a live USB to install the OS from. The problem is that the Disk Utility is missing from this pc, so I cant put the dmg image of Leopard on. I tried using Windows with TransMac Utility that formats the usb to the mac only standard and burns the image to it. But when I plug it in to mac its says that the usb is unrecognizable. Is there any other solution I can use to upgrade using USB stick?
thank you

Buy the retail copy of the Leopard installation disks ( the black set ) and install from there.

Cheers ... McBie

As McBie says the solution is to lash out, spend money and purchase Leopard for your friend. Second hand editions are available for about $100 on eBay and such. Buy a black retail install DVD only as no silver/grey version will work.