Try the following config file :
<configuration>
<configsections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net, Version=1.2.0.30714, Culture=neutral, PublicKeyToken=bbe994bc422bce0d" />
</configsections>
<log4net>
<appender name="FileAppender" type="log4net.Appender.RollingFileAppender">
<file value="LOGS\\log.txt" />
<appendtofile value="true" />
<maximumfilesize value="2MB" />
<rollingmode value="Size" />
<countdirection value="1" />
<maxsizerollbackups value="7" />
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%d|[%t]|%-5p|%c|[%x]| %m%n" />
</layout>
</appender>
<root>
<level value="ALL" />
<appender-ref ref="FileAppender" />
</root>
</log4net>
</configuration>
And the following line in your startup code :
DOMConfigurator.Configure(new FileInfo(@"log.config"));