Use the /AllUsers flag.

So is anyone who knows what to do to fix this issue going to answer it?

I have schools who would use our Unity3d created product but won't because their students aren't admins and can't therefore use it..

On windows, the unity webplayer installs for the current user only by default. This allows the installer to be usable without admin privileges which in general is a good thing.

However, this means that to install for all users, you need to run the installer with some options, and this requires admin privileges. You can do this via the command line as follows.

These are the full instructions to install the unity webplayer for all users on Windows:

1) Download the installer EXE (from http://unity3d.com/webplayer)

2) Open a command prompt using either of these methods:

• Clicking Start then Run, or:
• Press Windows+R, then type "cmd" and press return.

3) Drag the downloaded file into the command prompt window (this will copy the file's path into the window)

4) Add the options: /AllUsers /S after the filepath, so you end up with something like this in your command prompt:

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\Duck>C:\Users\Duck\Downloads\UnityWebPlayer.exe /AllUsers /S

5) Hit return. If you're not logged in as an admin user, you'll be asked to provide admin credentials at this point.

6) You're done. Because you used the /S flag for 'silent mode', there will be no feedback if the install was successful.