SQL Server log data is very important for any DBA to troubleshoot SQL Server related problems. In SQL Server 2000 there was no facility to check System and Application log, however in SQL Server 2005 there is facility of the log viewer. It is very useful tool and very easy to use as well.
In SQL Server 2005 all the windows event logs can be seen along with SQL Server logs. Interface for all the logs is same and can be launched from the same place. This log can be exported and filtered as well.
Following two images describes the how to launch log viewer and analysis the logs.
Following are kind of logs which can be viewed in Log Viewer.
Reference : Pinal Dave (http://blog.SQLAuthority.com)