You can also do it from the command line:
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Windows\system32>net config server /srvcomment:"Brian Hart's Notebook"
The command completed successfully.
You can use the computer description to identify who owns a computer without infringing on the company naming policy.
If you are on a Windows 7 system and cannot see the description, create a folder named "Network.{208d2c60-3aea-1069-a2d7-08002b30309d}" (without the quotes).
More info: http://blog.chrisara.com.au/2009/08/restoring-computer-description-in.html