I did what you describe, you want to know what happen 4 hours later? I was deleting files from another HDD which is where I installed all of my programs from win7. I use a software to help me delete all windows 7 program files and format. Restart, oh what do you know wont boot just black screen telling me nothing there....
My laptop was at work, so I didn't have a computer to redownload windows 8...
Anyways I had to wait for another of my friend to get home, went over to his house. I ask for his computer, commenced downloading win 8. Installed it to my USB and made it bootable.
Just save yourself the hassle get a USB tomorrow if not a DVD. Print out your KEY!!!
Save yourself the future hassle.