I tried installing Snow Leopard on my Late 2007 MBP with the installation disk I got with my 2009 MBP but I figured out that it wouldn't work because the installation disc would only work on the new machine not the old one. Anyway, now when I boot, I get the usual installation guide but the disk won't eject. I went to Disk Utility-->Eject Disk but it gave me a warning message that it couldn't be ejected because some applications were being used. I have no idea what that means and why it wouldn't eject the disc! Do you guys have any advice? Thank you!