system has failed because iertutil.dll was not found.

I've just solved the problem. Here's a tip that might be helpful. If you by any chance, after trying all the the methods mentioned here and couldn't get the problem sorted, then try this. 

1. Carefully select and then copy the following command:
   %windir%\ie8\spuninst\spuninst.exe
2. Open up the task manager
3. Type Cmd.exe, and then press ENTER.
4. Right-click inside the Cmd.exe window, and then click Paste to paste the command that you copied in step 1.
5. Press ENTER to uninstall Internet Explorer 8.
6. When the uninstall program is finished, restart your computer.

When you see a message like this:

Explorer.EXE - Unable To Locate Component : This application has failed to start because iertutil.dll was not found. Re-installing the application may fix this problem.

This will be in the Event Log:

Event Type:    Information
Event Source:    Application Popup
Event Category:    None
Event ID:    26
Date:        2/18/2010
Time:        8:38:48 AM
Description:
Application popup: Explorer.exe - Unable To Locate Component : This application has failed to start because iertutil.dll was not found.  Re-installing the application may fix this problem.

The iertutil.dll file is required for explorer.exe to start.  If explorer.exe is not able to run, you will not be able to do much with your system until the file is replaced.

The file could have been deleted accidentally, malicious software could have deleted it or your antimalware software could have quarantined it thinking it was a threat.

Describe your current antivirus and anti malware situation:  McAfee, Symantec, Norton, Spybot, AVG, Avira!, MSE, Panda, Trend Micro, CA, Defender, ZoneAlarm, PC Tools, Comodo, etc.

First here are all the things you can "try" that won't work:

sfc /scannow

The iertutil.dll is not one of the 3498 files that are protected under Windows File Protection so it will not be replaced automatically if it comes up missing.  This means that sfc /scannow will not help you.

It is also not on your XP installation CD for you to copy or expand.

You will have the same problem trying to boot into any kind of Safe Mode.

You will not be able to run a browser on the afflicted system to get on the Internet to download one.  There is also a great computer security risk in downloading files from Internet sites anyway.

You can still use Task Manager to run System Restore and that might restore it, but I have never tried it.

If iertutil.dll is missing, you can copy it from a working system to the afflicted system with the same version of XP and Internet Explorer or sometimes copy one in from another location on your system.

You can get a good copy and put it on a thumb drive, floppy, etc and copy it onto your afflicted system using Task Manager.

When you see the error, you can click past it and eventually get to your desktop background image where you can press CTRL-ALT-DEL to launch Task Manager. From TM you can click File, New Task, Browse and change the drop down "Files of type" to All Files so you can see all the files in all folders.

Browse/Navigate to c:\windows\system32 to see if iertutil.dll is really missing. If the error pops up again while you are browsing, click OK to get past it.  The explorer.exe is trying to run and can't until the missing file is replaced.

Then, still using Task Manager, browse to c:\windows\system32\dllcache and see if there is a copy of the file there.

If it is not in c:\windows\system32\dllcache, it is going to be elsewhere on your system and you can find it another way.
Start by looking in c:\windows\system32\dllcache.

If that is the only thing missing, you can just copy the file from c:\windows\system32\dllcache and paste it into c:\windows\system32 where it belongs.  If you don't find it, get one from a working system of the same type as yours, copy it to a thumb drive or floppy and still using TM, browse, copy and paste it where it needs to be.

From TM, you can still access your thumb or other even floppy media by browsing, copy, paste, etc. all work just fine. 

You use TM to browse to your thumb or floppy drive, copy the good iertutil.dll and then paste it into the c:\windows\system32 folder where it is supposed to be.

When you get going again, your system could still be afflicted so no matter what else you are using for malware protection,
do this:

Download, install, update and do a full scan with these free malware detection programs:

Malwarebytes (MBAM): http://malwarebytes.org/
SUPERAntiSpyware: (SAS):  http://www.superantispyware.com/

These can be uninstalled later if desired.

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