Download link: http://technet.microsoft.com/en-us/sysinternals/bb897553.aspx
What is PsExec? "PsExec is a light-weight telnet-replacement that lets you execute processes on other systems, complete with full interactivity for console applications, without having to manually install client software. PsExec's most powerful uses include launching interactive command-prompts on remote systems and remote-enabling tools like IpConfig that otherwise do not have the ability to show information about remote systems." [more]
I needed to reset some WSUS IDs on systems that were cloned in order to get them to check in to WSUS properly. I used psexec to run commands as though I were typing them into the PC locally to start/stop services, delete a registry key, and check for updates from WSUS Server in the following example.
psexec \\remotePC net stop wuauserv
psexec \\remotePC REG DELETE "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate" /v SusClientId /f
psexec \\remotePC net start wuauserv
psexec \\remotePC wuauclt /detectnow
You can also use this to run ipconfig and it will show you the results from the REMOTE system which could come in handy.