Resolved PLEASE HELP - Clean Install Snow Leopard Failed & Disc Stuck

Hi so I'm trying to do a clean install of Snow Leopard on an iMac mid 2007, 4gb ram 250gb HD. The iMac was working fine before, but when I tried restoring it to factory settings using original Snow Leopard install disc, going to Disk Utility, erasing HD, then clicking "install" for software, the software install keeps failing, it keeps saying "an error has occurred." I tried reseting the PRAM and reparing the drive through disk utility and trying to install again, but no luck. I think the disc was dirty but I can't even eject the disc! I tried command+E, using terminal and commad+s and typing "drutil eject" as well as holding F12 and left/right clicking mouse and nothing.. I can't even click anything else but the install disc upon set up. Please help me out to fix this, would appreciate it so much, thanks!

can't get the mac into that cmd+alt+o+f firmware, i'm using a non apple keyboard but pretty sure the keys still work the same as i use the windows symbol as the command key to get into that command+s screen.

Resolved! Tried holding the mouse button a few more times, this time with an apple mouse and before turning on the computer and the disc eject worked!