Windows 7 Tip: 
DestructingMessage.com is a free service which enables you to send a self-destructing message to someone. This means, once they read the message they will no longer be able to read it again after the timer has reached zero. This ensures your message is read by no one but the reader and all evidence of the message is erased.
Features
* Send self-destructing messages.
* Set the the message life time from 15 sec to 5 min.
* No registration or sign-up required.
Want to send a message to someone in a hurry? Don’t have time to login to email account, and compose? A great way to tease or have fun, with the peace of mind that it will not come back to haunt you.
Mike vutler
http://www.changeyourfuturetoday.net