You can't run Internet Explorer from the command-line or PowerShell like other programs, because it's executable isn't under
C:\Windows\System32. The variable
%SystemRoot%references the path
C:\Windows\System32, and is where things like Run and Powershell execute programs from by default because their paths start there unless specified otherwise. Internet Explorers execuables are found in:
C:\Program Files\Internet Explorer\iexplore.exe
C:\Program Files (x86)\Internet Explorer\iexplore.exe
You can execute Internet Explorer with the above paths or put these in a batch file:
%SystemRoot%\explorer.exe "C:\Program Files\Internet Explorer\iexplore.exe"
%SystemRoot%\explorer.exe "C:\Program Files(x86)\Internet Explorer\iexplore.exe"
Hope this helps.