|If you are booting to a CD or DVD it either works or it doesn't. It has nothing to do with the way the planets align or your current OS.|
Try them on another system just to see if they boot to the installer. If so your system may need repair. If not disks may be bad.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10