Why can't I drag/drop a file for editing in notepad in Windows Server 2008?

The inability to "drag and drop" from Explorer to an elevated Notepad window is a manfestation of the user interface privilege isolation (UIPI) feature. It's in the OS to prevent an less-privileged application from sending arbitrary "messages" (in the sense of operating system / application inter-process communication) to another, higher-privileged application. If the higher privileged application handled a message improperly it might be possible to for the less-privileged application to cause the higher-privileged application to execute arbitrary code on its behalf (these types of attacks are referred to as shatter attacks, so named in a 2002 paper describing the method of attack in then-current versions of Windows).

You can think of it a little bit like a "firewall" between applications running with a lower "integrity level" (unprivileged) and those with a higher integrity level (elevated).

If you REALLY want an elevated Windows Explorer, do the following:

• Start a command-prompt elevated and leave it open.
• Start Task Manager and elevate it by going to the "Process" tab and clicking "Show processes from all users".
• Highlight and kill all instances of Explorer.Exe using Task Manager.
• From the still-open elevated command-prompt window, enter "Explorer" and press <ENTER>.

Explorer will re-open elevated.

If you don't want to disable UAC, you could try just disabling UIPI (User Interface Privilege Isolation).

Open regedit and go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System

Add a new DWORD (32-bit) Value called EnableUIPI and set it to 0.

Restart the machine and see if it behaves as you want it to.

This was a problem on Vista, and I guess its made its way to server 2008 as well. Basically you can't run explorer elevated. You get the security option to do it, and it seems to have worked when you do so, but actually you still end up with a standard (non elevated) explorer window, hence the problem your having.

The workarounds I have had to use in the past have involved either using the save as explorer windows in your elevated notepad session, as this is also elevated, or using an elevated command prompt to create files, but none of these will fix your drag and drop issue obviously. Its a pretty crappy bug, that's been about for some time, I don't know why they don't fix it so you can run an elevated instance of explorer.