Windows search function has improved dramatically, but in the long run, I still occasionally find using the Command Prompt as, if not more, effective.
Fire up a Command Prompt (you may want to “Run as administrator” to be able to search everywhere). In that Command Prompt, type the following (each followed by the Enter key):
By default, the Command Prompt opens with C:\Windows\System32 as the “current” directory or folder. “CD” is the Change Directory command, and “\” indicates the top of the folder tree. This changes the current folder to the top of the C: drive, allowing us to search the entire thing.
DIR /s/p *.pdf
DIR is the “DIRectory” command, which lists the contents of that directory (aka folder). “/s” means list everything in the current directory and all sub-directories. “/p” means paginate – stop after each screen of results, so you have a chance to read it. “*.pdf” is what we’re searching for – in this case, any document that ends in “.pdf”, meaning all pdf documents.
The result will be a list of all pdf documents on your C: drive.
Change “*.pdf” to whatever you’re looking for. The results, as they say, may surprise you.