[Yzöwl]

If you are installing software/applications you cannot expect that each developers installer will have built in an error logging procedure which can be output through a command line interface.

For instance, Windows Installer uses the /L switch for logging to a file.

In some cases, you may be better advised outputting all to a log file then displaying that output to the console.

Also if it is only the error stream you are interested in have you tried changing the tee.vbs to read:

set con = createobject("scripting.filesystemobject").opentextfile("con:", 2)
do until wsh.stdin.atendofstream
        s = wsh.stdin.readline
        wsh.stderr.writeline s : con.writeline s
loop