Why cant I install Unity Player?

When I try to install Unity Player, a message comes up: Alert cannot be installed on this computer. I would like to know why this message might appear and what I might look into to fix this problem.

Moreover; may be the unity web player you are trying to install is not compatible with the Unity version installed on your PC…

I did have the same problem…The following link helped me to fix…

Note… after web player installation finished; go inside

Program Files>Unity>Editor

and Run the file

this was very important step for me to run unity web player