Hard drive voltage

This question isn't about a computer so I will not include any specs.
My friends and I are doing a project with an iPod. We are replacing the hard drive with a standard ATA computer hard drive. We have it all connected and everything but now one problem remains. We want to hook this iPod permanatly in my friend's car. Now the hard drive the iPod is now connected to needs some power. How can we hook it up to his car's battery. Best Buy has an adapter to switch DC (from the car) to AC (which the HD needs). The thing we are not sure about is how much power this hard drive needs. We are afraid if we give it all the 12V of the car battery we might fry it. Any suggestions?

 

This is the power requirements for a 75 GB IBM Deskstar 75GXP HD: http://www.pcguide.com/ref/hdd/perf/perf/spec/otherPower-c.html

You'll need a 5V DC and a 12V DC power source, not AC.

 

I think I will just convert the battery power to AC and plug a computer power supply in to it. Then I can just plug the HD into the power supply like you would on a normal computer.