Event viewer error

This is another error that is happening 45 times a day.....What do I have to do to fix it?Log Name: System Source: MicrosoftWindowsWindows Defender Date: 3/3/2007 11:01:30 AM Event ID: 3004 Task Category: None Level: Warning Keywords: Classic User: N/A Computer: IrvPC Description: Windows Defender RealTime Protection agent has detected changes. Microsoft recommends you analyze the software that made these changes for potential risks. You can use information about how these programs operate to choose whether to allow them to run or remove them from your computer. Allow changes only if you trust the program or the software publisher. Windows Defender can't undo changes that you allow. For more information please see the following: Not Applicable Scan ID: {1B1A7A33A51C47E1BD805B1B7C6A778D} User: IrvPC\Irv Name: Unknown ID: Severity ID: Category ID: Path Found: ieext:HKLM\Software\Microsoft\Internet Explorer\Extensions\{724d43aa0d8511d4990800400523e39a} Alert Type: Unclassified software Detection Type: Event Xml: <Event xmlns="schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="MicrosoftWindowsWindows Defender" Guid="{11CD958AC5074EF3B3F25FD9DFBD2C78}" EventSourceName="WinDefend" /> <EventID Qualifiers="0">3004</EventID> <Version>0</Version> <Level>3</Level> <Task>0</Task> <Opcode>0</Opcode> <Keywords>0x80000000000000</Keywords> <TimeCreated SystemTime="20070303T16:01:30.000Z" /> <EventRecordID>16785</EventRecordID> <Correlation /> <Execution ProcessID="0" ThreadID="0" /> <Channel>System</Channel> <Computer>IrvPC</Computer> <Security /> </System> <EventData> <Data Name="Product Name">%%827</Data> <Data Name="Product Version">1.1.1505.0</Data> <Data Name="Scan ID">{1B1A7A33A51C47E1BD805B1B7C6A778D}</Data> <Data Name="Unused"> </Data> <Data Name="Unused"> </Data> <Data Name="Unused"> </Data> <Data Name="Unused"> </Data> <Data Name="Domain">IrvPC</Data> <Data Name="User">Irv</Data> <Data Name="SID">S15211903812106242883966914321317281000</Data> <Data Name="Threat Name">Unknown</Data> <Data Name="Threat Id"> </Data> <Data Name="Threat Severity"> </Data> <Data Name="Threat Category"> </Data> <Data Name="FWLink">%%832</Data> <Data Name="Path Found">ieext:HKLM\Software\Microsoft\Internet Explorer\Extensions\{724d43aa0d8511d4990800400523e39a}</Data> <Data Name="Threat Classification Index">0</Data> <Data Name="Threat Classification">%%807</Data> <Data Name="Unused"> </Data> <Data Name="Unused"> </Data> <Data Name="Detection Type Index"> </Data> <Data Name="Detection Type"> </Data> </EventData> </Event>