Stopping people finding out uptime?

[Charlie Grosvenor]

Hi             If I port scan my machine nmap finds out how long my machine has been on for, How can I stop people outside my network from finding this information out?   Thankyou   Charlie --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.323 / Virus Database: 180 - Release Date: 08/02/2002