ShellRunas, a free utility from Microsoft that integrates into the Windows context menu to launch programs as a different user. It provides similar functionality to that of the command line based RunAs utility.

The command-line Runas utility is handy for launching programs under different accounts.

ShellRunas works on Windows XP, Windows Vista, Windows Server 2003 and Windows Server 2008.

To use this tool, download it here.
Extract the Zip-File.

Run shellrunas.exe /reg from the directory where you extracted the files.

Shellrunas.exe will be registered and you can now select Run as Different User from the context menu.

Using ShellRunas

Usage: shellrunas [/reg | [/quietreg ] | /regnetonly [/quiet] | unreg | [/netonly] <program> <arguments>

/reg : Register ShellRunas shell context-menu only
/regnetonly : Register Shell / netonly context-menu entry. (note: a command promt will flash when the
                       program starts.
/unreg: Unregisters ShellRunas sheel context-menu entry.
/netonly: Use if specified credentials are for remote access only.
<program>: Runs program with specified credentials and parameters.