You may have a Windows update that has not finished installing. Windows will prevent software from being installed until the update has finish. Usually this type update requires you to reboot the system, so it can finish installing.
Thanks very much for this. I hadn't thought of that. I have rebooted the system, but have lost Team Viewer obviously, so will have to wait for Monday now to check out if this is correct.
Team Viewer is great.
Windows will give an option to reboot installing updates and an option to reboot without installing updates, just make sure the updates are installed. A reboot without the update installing will still result in not being about to install software.
Quick update, it transpired that the user I was installing on didn't have admin privileges, but this wasn't flagged at all. Logging in as admin and doing the install did the trick and all running smoothly now.
Thanks Schamblee for your tips. They certainly were very useful.