Windows 8.1 stuck on gray "wait" screen - Auto repair and System Restore won't work

I have a Dell laptop Inspiron 15R 7537 that came with Windows 8. Yesterday I upgraded to Windows 8.1. Everything seemed to work fine after the upgrade. I shut down and re-booted several times with no issues. When I turned the computer on as usual today, I got the log in screen, then it briefly went to the desktop, then came a gray screen that blocks 99% of the desk top. This gray screen says "please wait" and has a cancel button at the bottom. It hangs forever and the cancel button doesn't work. It gives no other information. I read several threads on the Microsoft Windws forum and this seems to be a common problem. One thread suggested to boot using the Windows 8 recovery media disk that came with the Dell computer. I selected Troubleshoot, then Advanced Options, then Automatic Repair. I got a message that it couldn't do an automatic repair, so that didn't work. Next I tried System Restore, but I got a message that there were no restore points available from which to restore. Just to clarify - the Recovery Media Disk I have from Dell is for Windows 8 - not 8.1 - so maybe that's the problem. The computer is totally worthless the way it is now, so unless there is some fix for the hanging gray screen in Windows 8.1, I would be happy just to reload the original Windows 8 Operating System. At least that worked. I have average computer knowledge, but am not a techy by any means. Can someone please explain to me, in basic language, how to reload the Windows 8 Operating System on my computer using the Dell recovery disk. I would really appreciate it. Thanks.