What should I do when a "User Account Control" Window appears?
Don't worry. This Window only occurs once. PhotoSync needs access to the Windows Firewall and it is adding your user account to a system wide list to allow the communication between your Windows Computer and your iPhone/iPad/iPod Touch. Both actions require Administrator access and that's what this Window is asking for:
As you can see in the Window touchbyte GmbH is a verified publisher. PhotoSync comes with a signed trusted certificate that was issued by GlobalSign ObjectSign CA.
You must answer this Window with Yes and if necessary confirm this action by entering valid Administrator privileges (only if your user account isn't an Administrator account). If you do not answer with Yes, PhotoSync Companion will not run and you will get the Window the next time you start PhotoSync Companion.