When you are prompted, click Open, and then click Extract Now.
In the files that you extracted, double-click cleanup_tool.exe. If you are prompted for an administrator password or for confirmation, provide the password, and then click Continue.
In the Do you want to run the .NET Framework Setup Cleanup Utility? message, click Yes.
Click Yes to accept the license agreement.
In the Product to cleanup window, click the list, select .NET Framework - All Versions, and then click Cleanup Now. Note The cleanup tool does not let you remove the .NET Framework 2.0 in Windows Vista or later versions of Windows because the .NET Framework is installed as an operating system component.
After the .NET Framework is removed, restart the computer.
Visit Windows Update again, and then check for and install updates.
Try to reinstall the .NET Framework update.
Other .NET Framework update installation issues
You may also experience the following issues when you install .NET Framework updates:
The update is not installed.
The system keeps reminding you to install this update even though you have already installed it.
The desktop does not appear.
Resolution to these installation issues
If you experience one of these issues, try the following methods to resolve the issue.
Method 1: Download the update from the download link and install it in clean boot mode
We suggest that you install the updates in clean boot mode to avoid interrupting non-Microsoft programs. To enter clean boot mode on a computer, follow these steps:
Click the Start button, type msconfig in the Start Search box, and then press Enter. If you are running Windows 8 or Windows 8.1, type msconfig on the Start screen, and then press Enter.
If you are prompted for an administrator password or for confirmation, type the password or click Continue.
On the General tab, click Selective Startup.
Under Selective Startup, clear the Load Startup Items check box.
Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
When you are prompted, click Restart.
After your computer restarts, try to update your computer again.
For more information about this method, see the following article in the Microsoft Knowledge Base:
331796 Perform a clean startup to determine whether background programs are interfering with your game or program
If you are not installing the .NET Framework updates when you receive error code 0x80070643 or 0x643, you may have to collect additional logging information to troubleshoot your issue. These logs can be reviewed by support professionals or IT professionals to help determine the issue.
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