Install Os X after overwritten by Windows?

[Phasebook]

Hey guys,
I have a strange problem and I am not sue if I am posting in the right group...
A friend of mine has one of the old iMacs(2007-2008 A1224 20'') and he gave it to someone to fix a problem with the OS. This smartass installed a fresh copy of WIndows 7 by overwriting the current OS X and windows(he was using Bootcamp and rEFIt for booting both Windows and Leopard). Now when you turn on the ocmputer there is no Apple logo or boot manager, just a white screen for some seconds and after that it starts booting Windows...
Is there a way to get back to Os X? The owner is missing the original disk, so can you give me an advice if a new retail disk is bought, would it work and which one should he buy?
I would be glad if people with similar problem share some experience...

 

[Weaselboy]

Just call Apple at 1800MYAPPLE and give them the model number and they will sell you the grey OEM installer disks specific to that Mac. Then you can boot to that DVD and use Disk Utility to reformat the drive and install OS X.

 

[Phasebook]

Just call Apple at 1800MYAPPLE and give them the model number and they will sell you the grey OEM installer disks specific to that Mac. Then you can boot to that DVD and use Disk Utility to reformat the drive and install OS X.

Thanks, I will definitellydo that tommorow, it sounds like the best thing I can do

 

[Mr Hildy]

Well put. Just to add a little more detail to what was said above: When you get your disc, turn on the Mac and hold down Command + R until it takes you to the menu screen with Disk Utility. From there, insert the disc and proceed to format your hard drive to "OS X Extended (Journaled)" and re-install OSX.

Good luck!