In Panther]
1. Open Disk Utility
2. Click Image and then Convert
3. Select the bootable .dmg and click Open
Double-clicking the .dmg without locking it first almost certainly will kill the boot functionality. Download again.
A .img file no longer exists in OS X (unless you purposely convert it to that format (NDIF I believe). What you get when you mount a disk image (also the .img ones), is a volume.
4. Make sure the image format is "DVD/CD Master" and save your new image (This will yield an image called [yourname].cdr)
5. Open Toast and click and hold the Other menu option.
6. Select Disc Image and then drag [yourname].cdr onto Toast and select mount.
7. Click and hold the Other menu option again, but this time select Mac Volume.
8. Click the Select button and choose the mounted .cdr image you made.
9. Uncheck all the options in the pop up window (make sure optimize or autostart are NOT checked). Check the bootable option. Don't worry if it gives you a warning saying there is no system folder and so it will not be recognized as a startup disk (it is wrong).
Aside: the optimize option is what really fucks over your disk making it unbootable.
10. Press Record. Wait.
11. Restart and hold down the "C" key.
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This could also work in Jaguar. Just use Disk Copy instead of Disk Utility. And don't forget to save as DVD/CD Master.
This method is successful in burning a bootable Panther 7B85 installation disk.
