This is an extension of the question on SO
If I see a process being run as "NT AUTHORITY\SYSTEM" account, can I start a program with "NT AUTHORITY\SYSTEM" credentials? Something like run as option.
You can use PsExec to run a command in the System account.
Example:
Run Regedit interactively in the System account to view the contents of the SAM and SECURITY keys:
psexec -i -d -s c:\windows\regedit.exe