Windows 8 - update installed - windows won''t open

I am writing this on behalf of my husband who isn't able to use his computer due to the fact that Windows won't open. He upgraded to Windows 8 from Windows 7 a couple of days ago and has had nothing but trouble, from the installation itself to programs not working, and now this.
When he switched on his computer it said that it was installing updates, but after it re-booted it went through the loading up, as far as showing the new Windows logo, then nothing. The screen is completely blank. He knows the hardware is OK from the mini screen on the PC.
He would like to know if anyone else has had a similar problem and if so, how to resolve it.

Has he got the win8 installation iso on dvd /usb?

Yes. Since my posting, he has been able to do a Windows Repair and he did this by installing again from the USB flash disc. It is currently backing up all the files, so we are keeping our fingers crossed it all goes well. He has said that once everything is backed up he is going to un-install Windows 8 and reinstall 7. [I think I will emigrate while this happens!!!].