i can help here...
checklist:

=> Make sure your disk is bootable (get the software IsoBuster, install, load cd and see if a bootable selection comes up in the left panel...)
=> Configure your BIOS to load the CD as first priority
=> Put the cd in the drive before you turn on your computer (the easiest way to do this if you are doing a cold start [just turning on your computer] is as soon as your computer starts to load up the BIOS, put the CD in your drive and then restart your computer)

hope this helps

PS: did you check your download with the MD5 checksums it came with to make sure your download is complete...