Microsoft Windows [Version 6.0.6002]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.
C:\Users\wfsp>msg
Send a message to a user.
MSG {username | sessionname | sessionid | @filename | *}
[/SERVER:servername] [/TIME:seconds] [/V] [/W] [message]
username Identifies the specified username.
sessionname The name of the session.
sessionid The ID of the session.
@filename Identifies a file containing a list of usernames
+,
sessionnames, and sessionids to send the message
+ to.
* Send message to all sessions on specified server
+.
/SERVER:servername server to contact (default is current).
/TIME:seconds Time delay to wait for receiver to acknowledge m
+sg.
/V Display information about actions being performe
+d.
/W Wait for response from user, useful with /V.
message Message to send. If none specified, prompts for
+ it
or reads from stdin.
update: I dread to think what you've done to your vista box :-)