Modifying an OpsMgr Agent on Windows 2008 server

When modifying an OpsMgr Agent installation on a Windows 2008 server it can’t be done from the Control Panel since UAC is blocking it. So it has to be done in a different manner.

The start for both versions of OpsMgr (SP1 or R2) is the same: start an elevated command-prompt. Afterwards it is different:

1. OpsMgr SP1:
   msiexec /I{768DB8BD-CB3A-43F4-9A4C-BA2921D27AD3}
   
   
2. OpsMgr R2:
   msiexec /I{25097770-2B1F-49F6-AB9D-1C708B96262A}

Now the OpsMgr Agent installation wizard will start.

Source: OpsMgr Forum, this thread.