This basic tool lets you find Win32 errors by name, number or description.
Looking-up errors by number can be useful when a program returns an error code without a description. (While other tools already do that, this one has the nice feature that you can type a number without knowing/caring if it's hex or decimal and get back matches for both possibilities.)
Looking-up errors by description can be useful when you're writing code and want to find an appropriate error value to return in a given situation. You can search for errors containing words/substrings, using basic AND/OR boolean logic. Double-click a line in the results to copy that error's name to the clipboard.
The source is only useful to programmers who wish to modify the tool. The tool was thrown together using C++ and MFC while watching TV so don't expect anything elegant. Searching is done using brute force because it's fast enough (the bottleneck isn't the seach, it's updating the results listview).