XeLaTeX runs slow on Windows machine

I've been wrestling with the same issue too after upgrading TeXLive from 2013 to 2016. Each compilation started to take over a minute and the process monitor showed a lot of font files being read.

Running fc-cache.exe from the LaTeX distribution's bin folder (as indicated by the comment above) fixed the issue without reinstalling TeXLive.

Please note that the distribution's texmf-var\fonts\cache folder needs to be writeable to the user running fc-cache.exe.

Another solution is to change the properties of xelatex.exe so that it runs as administrator always. (Right click on the file in the bin\win32 folder, then click on the Compatibility tab, and click box at bottom to "Run this program as an administrator.")

This then required that I elevate TeXnicCenter to run as administrator, too. After making these changes, the problem may go away.

This is similar to what has already been posted, but not identical, so here goes.

If none of the other answers are working for a future reader, try running fc-cache -f (thanks to Hao and Ulrike Fischer for this solution) in a directory that looks something like D:\texlive\2016\bin\win32 (which is exactly what it was on my machine, I run Win10) or -- provided your PATH^a is set to it -- anywhere else on your computer will do just fine. This worked for me.

This solution seems to not have worked in another, still unresolved case.

^{a: If you don't know what that means, don't worry about it right now. You can worry about that when you try to install the newest vanilla TexLive and have to set your paths manually. Which is fun to do, provided you have time to learn the ways of the jedi.}