Have you ever tried to use Windows Explorer to create a folder within or copy a file into a protected folder such a Program Files or Windows and had to deal with the confusing “File Operation” dialog box before you could complete your task. This is one of the most confusing and poorly understood features of User Account Control.
When running as a administrator with UAC enabled, your standard user token does not have write permissions to these protected folders.
Unfortunately, because Windows Explorer was not designed to run in multiple instances in the same desktop session, Windows cannot simply throw up a UAC prompt and then launch an elevated instance of Explorer.
Instead, you get one or more elevation prompts (if full-prompting is enabled) and Windows completes the operations using the full administrator token. This can be annoying if you have to make repeated operations in these folders.