Hello. When I was trying to update my Windows 7 for Windows 8, at the end of the process appear a error and my computer restart. Now, when I turn it on appear the logo of the Windows and the circle that indicates it is loading, but the screen turn black and takes a while when appears the blue screen indicating that was an error and my computer will reset. The error code is 0xc000021a. I don't have a dvd with the Windows 8. I downloaded the upgrade from Microsoft website. Sorry about my English.