I decided to upgrade my pc from win 7 ultimate 64bit to win 8.1 Pro 64bit. However, on booting from the dvd (I used an external drive which is working perfectly), after the "press any key to boot from cd/dvd" screen the screen goes blank and nothing happens at all. I tried using the internal dvd drive and got a blinking cursor instead of the blank screen after which nothing happens. The installation proceeds successfully on my other two laptops with the same external drive and the same disk. Please help.