Microsoft provides a useful command-line tool called err.exe that can help you find the meanings of error codes. When you run err.exe and specify an error code, the program searches all the error-code definitions from the various header files that Windows uses to generate a list of possible error meanings. You can download err.exe at Microsoft Web site. (Although the Web page is called "Exchange Server Error Code Look-up," err.exe actually handles Windows OS error codes.) [more]
If you run err.exe and specify an error code--for example,
err 1645
the output looks like this:
C:\temp\Err>
# for decimal 1645 / hex 0x66d :
ERROR_INSTALL_REMOTE_PROHIBITED winerror.h
# The Windows Installer does not permit installation from a
# Remote Desktop Connection.
# for hex 0x1645 / decimal 5701 :
NELOG_NetlogonFailedToUpdateTrustList lmerrlog.h
SQL_5701_severity_10 sql_err
# Changed database context to '%.*ls'.
# 3 matches found for "1645"
Notice that err.exe searches for the value you entered in both its hexadecimal and decimal forms.