Unable to verify sketch which contains 3rd party library Timer1

I'm using IDE 1.6.12 on a PC running Windows 10
Each time I try to verify or upload a sketch which contains "#include <Timer1.h>" I get the following error message:

"C:UsersAlan.Alan-PCDocumentsArduinoMk2_bothDisplays_4.inoMk2_bothDisplays_4.ino.ino:58:20: fatal error: Timer1.h: No such file or directory
#include <Timer1.h>
** ^**
compilation terminated.
exit status 1
Error compiling for board Arduino Mini."

My PC library entry is the following

"In This PC/Acer(C:)/Program Files (x86)/Arduino/libraries/TimerOne

_MAXOSX Filefolder
examples Filefolder
keywords Text Document
TimerOne.cpp CPP File
TimerOne H File"

TimerOne was downloaded as a zip file and expanded and coped in to the folder TimerOne.
I have tried reinstalling the IDE, re-downloading the library all without success.
A few weeks ago I was able to verify sketches which contained Timer1.h but now it doesn't work anymore.
Please help.

Please post the full contents of the error message.

Note also that you say you've installed a library called TimerOne, yet the error is in reference to a library called Timer1. These are not the same thing.