Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
What model iMac?

Yes, if you boot the Mac into Target Disk Mode, and attach it to your PC (via Firewire), it will appear as an external HD. However, you'll either need to reformat the drive to a Windows compatible format, or install MacDrive on the Windows.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.