My advice is to simply install the platform update for Windows.
You are most probably running something like Windows 7 SP1, which is well out of date. You should install the updates anyway as there will be many security patches you are missing amongst other things. I think the reason Kodi requires the update is for the updated Direct-X version. But either way, the operating system updates will let you install the newer version of Kodi.
It is always recommended to get all the updates for your windows version. You should also update all your drivers. I use the free version of Iobit Driver Booster for this task. You'll be amazed how may drivers need updated.
Thanks for info . Also , i've been told on this forum that I can just install 17.3 over 16.1 i've also been told elsewhere I have to un-install 16.1 first. I don't want to mess it all up . Can I just install 17.3 over 16.1 and retain all my addons and settings.
All your advice is much appreciated , years are not on my side.
There should be no problems installing 17.3 over 16.1 without removing first. Best thing is to first backup your userdata folder before you do the update. This way, is something goes wrong with the installation, you can bring back your userdata folder.