Why is it saying that I may have insuffecient privileges to start the Aple MObile Device Service whe I unistall and reinstall the 64 bit version of Itunes on my PC?

I am trying to update my sons iphone and Itunes was not recognizing it in the panel as a device, so I read the support instructions on this and follwed all the directions. I first tried to just go to services on my computer and stop and restart the Apple Mobile Device Service, but that did not work. So I uninstalled all Itunes and apple and Bonjour and Quicktime programs from my computer and am attempting to download Itunes back onto my computer and I am getting this warning message that Apple Mobile Device cannot download b/c I may not have priveleges. What does that mean and how do I get past this to get Itunes back on my computer? I need the AMDS in order for Itunes to sync my phones and Ipad. So why isnt it letting me download it? Help!!!!!!