Totally clueless. NEED HELP.

Well my iMac Late 2008 wasbootcamped to Win7 (32) and Mac and the Mac partition got corrupted so I formatted it. Afterwards, I turned the Mac partition into unallocated space and tried to merge it with the Win7 one. While it was moving the files in the Win7 partition, the process had an error. Now I can't boot into Windows and Mac is gone. What steps should I do to start again from scratch? (Clean Mac)