Try these suggestions which seemed to work more times than none.

Suggestion 1: Clean up Windows Update temporary folder ===========================================
1. Click Start, Run, type: cmd and press Enter. Please run the following command in the opened window.

2. Net stop WuAuServ

3. Click Start, Run, type: %windir% and press Enter. In the opened folder, rename the folder SoftwareDistribution to Sdold. Click Start, Run, type: cmd and press Enter. Please run the following command in the opened window.

4. Net start WuAuServ

5. If the issue still persists, please move on to suggestion 2.

Suggestion 2: Reinstall Windows Update Agent 3.0

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1. Please download the file at Windows Update Agent 3.0

2. Save the file to C: drive.

3. Click Start->Run, type: "C:WindowsUpdateAgent30-x86.exe /wuforce" (without quotations) and then press Enter to install the Windows Update engine

4. There is a space between "C:WindowsUpdateAgent30-x86.exe" and "/wuforce"

5. Note: If you are using Windows Vista, please save the downloaded file to the D: drive, because the file cannot be launched directly from the C: root directory.

6. If it still does not work, please proceed to suggestion 3 to reinstall Windows Installer 3.1.

Suggestion 3: Reinstall Windows Installer 3.1

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1. Press Start and choose Run.

2. Type in "cmd" (without quotation marks) and press OK.

3. In the command line, type in the following command and press Enter: MSIexec /unregister

4. Then, type in the following command and press Enter: MSIexec /regserver After finishing the above steps, please check the result again. If the issue persists, please click Start, click Control Panel, and click Add/Remove Programs to check if Windows Installer 3.1 has been installed. If it has, please highlight and remove it. After that, please reinstall Windows Installer 3.1 from the following link. Windows Installer 3.1 Redistributable (v2)