Cant find power cable for my new hard disk

hi buddies,
i just bought a brand new hard disk toshiba 500gb but when i got home i noticed that the actual power cable that fits in the existing hard disk isnt the same for this hard disk. the other data cable directly fits into the motherboard but with the 4pins molex cable i cant connect it in the hard disk. so actually i have a hard disk without power and i really dont know what to do as i have ordered it on the net and if someone could help me that would be kind..
thank you