Dealing with xpcom_core.dll Application Errors

What is xpcom_core.dll?

Xpcom_core.dll is related to the Liveconnect or XPconnect plugin which was used to support ActiveX on Netscape and Mozilla browsers. At present, the plugin which includes the xpcom_core.dll file is outdated and not in use.

What are the errors generated by xpcom.exe?

The errors used to be generated majorly during browser startup as this was a plugin. Some of the errors displayed on the screen were:

  • ‘Cannot start [APPLICATION]. A required component is missing: xpcom_core.dll. Please install [APPLICATION] again’.
  • ‘This application failed to start because xpcom_core.dll was not found. Re-installing the application may fix this problem.’
  • ‘Cannot find [PATH]\xpcom_core.dll’
  • ‘Xpcom_core.dll Not Found’
  • ‘The file xpcom_core.dll is missing.’

Software affected because of the xpcom_core.dll error

The browsers using the ActiveX plug-in which had the xpcom_core.dll file was used by:

  • Netscape
  • Mozilla 1.x and earlier versions

The browsers were used on systems running Windows XP and 2000.

How to fix errors generated by xpcom_core.dll?

Xpcom_core.dll is part of an ActiveX plugin on the Mozilla browser as Mozilla does not support ActiveX. When the browser was started, the plugin was loaded first, and this is when the error was generated. To fix the error, follow these methods-

1) Restore your system

2) Uninstall the ActiveX plugin

3) Delete files related to the plugin

Restore your system

This method will work only if you are using Windows XP and if the problem appeared just after any plugin or software installation. If it is running any other Windows OS before XP, it is better to skip to the next method. To run system Restore, follow these steps:

  1. Click on Start and go to All programs
  2. Choose Accessories and move to System Tools
  3. Click on System Restore
  4. From the list of dates, choose a date when the browser was working fine
  5. Click Next to apply the settings of the date chosen and restart the system

After this, try opening the Mozilla browser, and if it still gives the xpcom_core.dll error, go to the next method.

Uninstalling the Plug-in

To uninstall the plugin, follow these steps –

  1. Click on Start and choose settings
  2. Go to Control Panel
  3. Choose Add or Remove Programs
  4. From the list, choose XPconnect or Liveconnect plugin
  5. Choose uninstall

After this, close all programs and restart the system. Now start the browser, and if it still gives you an error, then follow the next method.

Delete the file related to the plugin

To delete the plugin files, follow these steps:

  1. Close the browser and then click on Start and go to Search
  2. In the search box, type npmozax.dll and scroll down and click on Advanced Options and check the Hidden files and folders option
  3. Once the file is found, delete it, also look for plc4.dll. plds4.dll, nspr4.dll and delete them

After deleting the files, it is better to uninstall the existing browser and reinstall the latest version. You can also use the program uninstaller software to uninstall the Mozilla browser with all the plugins.