You should check out err.exe available from http://www.microsoft.com/downloads/details.aspx?familyid=be596899-7bb8-4208-b7fc-09e02a13696c. Don't be tricked by the name (Exchange Server Error Code Look-up) because it supports error codes other than Microsoft Exchange.
It is very easy to easy, and supports “bidirectional” search. It can look up the meaning of an error from an error code, and vice versa. It supports many Windows common header files. Please let me know if you are aware of other error lookup tools.