Perhaps the disc was an issue - try another one, but this time burn it at 4x speed, no faster than that. If you still get those problems, try this technique using a USB thumb drive instead:
Use this tool to make a bootable USB (must be 4GB in size) using the ISO you downloaded: Universal USB Installer – Easy as 1 2 3 | USB Pen Drive Linux
Ensure that the PC can boot from a USB drive by checking that in the BIOS settings. Insert the USB, turn on the computer, and it will boot from the USB drive. Now install Windows 7 as normal.
Let us know how you get on.