I sounds like the downloads, or the Burns are not working correctly. I suppose the usual suggestions are in or order for using a slow burn speed, and good Media.
You might also try downloading the .iso for the following location and of course check your bit version.
Do you believe the problem with Vista is in any way relevant?
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There are some DVD players that have problems with Windows 7. If you were running Vista, they should be about the same, but you might think about using the flash drive installation if you can't get the system to read the DVD your burn.