Problems With Windows Installer 3.1

Windows Update Error
If you are attempting to download Windows updates and receive Error 0x80070420, you must install Windows installer 3.1. The error may also be a result of a corrupt install of the installer and it must be reinstalled. If you have previously installed the Windows installer, first uninstall it, then download a new install from Microsoft's website. Verify the install by choosing 'Start,' then 'Control Panel' and 'Add/Remove Programs.' A list of installed programs is displayed. Search for Windows Installer 3.1. If the program is located, uninstall it by choosing 'Remove.' After the program completes the uninstall process, restart your computer. If the program is not listed in the listed of installed programs, visit Microsoft's website and download the file. After the file has downloaded, double-click on it and install it to your computer. After the install completes, restart your computer. Attempt to install the Windows update and verify that you no longer receive the error.
Windows Installer Service Error
Attempting to install a software program on your computer can result in the error message 'The Windows Installer Service could not be accessed' if the Windows installer is not functioning properly. It is possible that the installer is corrupt or the service may be disabled. Verify that service hasn't been disabled by choosing 'Start,' then 'Run.' Type 'Service.msc' in the 'Open' box. Next press 'OK.' This opens the 'Services' dialog box. Locate the Windows Installer service and right-click on top of it. A submenu will display. Choose 'Properties.' Locate 'Startup Type,' click the down arrow and choose 'Manual' and then 'OK' to close the dialog box. Right-click on top of the Windows Installer and choose 'Start.' This will allow the service to start. Attempt to reinstall the software and verify that you no longer receive the error. If the issue hasn't been resolved, uninstall the Windows Installer using the 'Add/Remove Programs' menu, download an updated Windows installer from Microsoft's website and install it to your computer.
Program Conflict
Programs running on your computer may interfere with the installation of Windows installer and result in an installation error. Disable programs by choosing 'Start' and then 'Run.' Enter 'Msconfig' into the 'Open' box. Then choose 'OK.' This opens the 'System Configuration Utility' dialog box. Choose the 'Startup' tab, then 'Disable All,' then 'OK.' Attempt to install Installer. After Installer installs successfully, reenable the start-up programs by accessing the 'System Configuration Utility.'