Problem Installing Adobe Flash Player

I am trying to install Adobe Flash Player on a PC running Windows Vista. 

During installation, at about 50% through, it asks me to close Skype, but although I do have skype on the PC, it is not open.  The installation process will not continue beyond this point.

I have tried opening Skype and the closing it, but this makes no difference. The Windows Task Manager confirms that the Adobe Installation programme is the only sofware running.