First I suggest that, if possible make every effort to backup any critical data presently on your PC.
Then boot from the install media (set bios boot device options to DVD #1) and perform a clean install and if possible use the advanced options regarding where to install it and clear your hard drive of any existing partitions so all availabe space has an unallocated designation. NOTE: If it is a laptop, you may wish to preserve the manufacturer's system recovery partition, it's up to you.
If the problem persists, then we need to assess the media itself, inspect for smudges and or scratches. What is or was the source of the media? If it's a downloaded ISO, then reburn it using the slowest possible settings (4x or slower) that your burning software supports.
Consider an issue with the source drive (laser, cable or even drive mechanics) could be an issue. Try the install, using another source drive (DVD or perhaps even a thumb drive).
Make sure to detach or remove any extraneous peripherals during the install, keeping any potential external hardware issues to a minimum.
Keep us posted and if you can described any specifics as to where you are in the process
