It must be possible in theory to copy it to CDs with a Wintel box, but I don't anticipate it being straightforward. At all. It takes two CDs to install Panther, (three if you want the dev tools) and you don't know what goes on wjich disc, or how to tell the installer to ask for the next disc etc.

You're going to need a Mac-bootable DVDROM. Maybe you could borrow the one from your PC in the hope it will boot your Mac. But you'll have to attach it to the cable where the HD is currently, which would mean running it outside of its case. Also of course, you would then have no HD attached, so you'll need a firewire enclosure for it in order to install the OS. Thats the cheapest way, but of course its a pain, and there's no guarantee your PC DVDROM will boot the iMac.

Best bet is either a DVD from another iMac, or an external firewire DVDROM. Failing that you can try putting your new OS in a friends Mac and installing the OS from that one before you put the drive in the iMac. Again, there is a chance this will not work depending on what kind of Mac you borrow for the install. If you can get a PowerBook or iBook with DVD, you should be able to use the DVD via firewire to install on the iMac.

Most of these solutions seem to involve firewire, so if your iMac doesn't have it, that will restrict your choice severely.