[Microsoft] Use the Error Code Lookup tool to determine error values from decimal and hexadecimal error codes in Microsoft Windows operating systems. The tool can look up one or more values at a time.

While the download name is the “Exchange Server Error Code Look-up”, this actually has error codes for all of Windows. In fact, yuo can even do a ‘reverse’ error lookup:

D:\>err =ERROR_FILE_NOT_FOUND
# matching string “ERROR_FILE_NOT_FOUND” :
0×00000002 ERROR_FILE_NOT_FOUND           winerror.h

Very cool, and extremely useful.