Yahoo Spy Monitor allows you to log chat conversations and block messages from unwanted people.
Monitor your spouse:
Have you suspected that your spouse is cheating on you? Why he/she cleans the MSN conversation tracks on the computer? Now with the MSN Spy Monitor, he/she can’t hide anymore.

Monitor your employees:
Is your employee working or playing? Have you noticed a drop in productivity? Now you can know the truth about what they are talking about through MSN with MSN Spy Monitor.

Yahoo Messenger Spy Monitor features:

Works in stealth mode, silently and smoothly.
Automatically capture incoming and outgoing chat conversations.
Block unwanted people with customized contact list.
Filter message content with customized keyword list.
Support Yahoo Messenger, ICQ and AOL.
Easy to setup and use.
Export logs to HTML EXCEL format.
Send logging reports in text format to a pre-set email box .
Runs absolutely invisibly under Windows systems. Only you can call out and close the program.
Works on Windows 2000/XP/Vista, Windows Server 2003.