you've ruled out a checksum error in your downloads by performing the md5 checksum comparison. you've (mostly) ruled out defective dvd-r media and a defective dvd burner by taking the next step and using probably unetbootin to deliver the ISO file to a usb pendrive. you've ruled out defective usb pendrive (mostly) by the simple fact that unetbootin or whatever utility you used to create it completed creating the pendrive correctly. try the pendrive in another machine. i suspect you will not find it to be the problem.
i assume you have 2 4gb ram cards, so you may have removed one, retried and then should have removed the other prior and reinstalled the first one you removed for one last try. you've taken good steps to rule out many of the possible issues so far.
try this: http://seagate.custkb.com/seagate/cr...271&NewLang=en
it will work on non-seagate drives as well to test for defective physical media/hdd. ruling this out could be easiler than looking at whatever issue may have occured with the bootloader/partition table or just fully wiping it out of frustration.done that.. and more likely,given that it's a very new machine. you tend to discover legitimately defective harddrives very quickly.
hope this helps. my only other advice is if you are getting heated, turn it off and just go think about it. come back refreshed with a new set of eyes, and you'll remember the one stupid step you skipped over diagnosing it.