After updating to Lion, can't re-install Snow Leopard or Lion Here is my situation: I have a 2010 iMac that came with a Snow Leopard disc, which I installed. Then, when Lion was released, I upgraded to it. However, yesterday, I had to erase my entire HDD (because of a permanent kernel panic due to the removal of some vital OS stuff). 

The problem is that now I can't install Snow Leopard again (so that I may upgrade to Lion) or install Lion without downloading it (my connection is VERY slow, it would take over a week possibly). I tried using the Snow Leopard disc, which I confirmed to work on a Windows machine, to install it. However, it just ejects the disc on my Mac, going to the new Lion thing after boot (where you can install it by downloading from Apple's servers). It does the same with a Lion disc that I burned myself. Holding C won't help, and the discs won't appear on the option boot screen. 

What should I do? Is there any way to revert the firmware back to pre-Lion, so that I may install Snow Leopard and then upgrade? 

Note: I only have a Windows machine working, not another Mac.
Firmware shouldn't have anything to do with it. I was able to install SL while I had Lion on. Maybe there is some problem with your disk drive on Mac? 

I haven't tried it but you might be able to use the disc from a network device but you will have to find more info on it. Also you might be able to revert the system sometime back using Time Machine. Have you looked into that?