Hi
I've used Agent Ransack for years as my search software.
I still do in Windows 8, it works and it's free.
I have seen times when the Windows search engine couldn't find a file that I was sitting and looking at in Windows Explorer.
As far as I can tell if it's there Agent Ransack will find it.
http://www.mythicsoft.com/agentransack/download
It's easy to use, and will be added to the right click dropdown so all you have to do it right click on the location you want to start the search from and type in what you are searching for.
Mike