The default location for the Sharepoint (2007 / 2010) log files might make sense when you finally locate them, but remembering it at the time you need them the most is not that easy.
Sharepoint 2007 + log files + location =
C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions12LOGS
Sharepoint 2010 + log files + location =
C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions14LOGS
Now, when it comes to reading the bloody thing you’re on your own……..