Fix: Windows 11 Installation Error 0xC1900101 – 0x40021

Many Windows users are running into the 0xC1900101 error when they try to upgrade to Windows 11. Depending on the underlying cause, the error can show up in a few different ways:

• 0xC1900101 – 0x2000c
• 0xC1900101 – 0x20004
• 0xC1900101 – 0x20017
• 0xC1900101 – 0x40017
• 0xC1900101 – 0x30018
• 0xC1900101 – 0x40021

Today, we will talk about how to fix the Windows 11 installation error code 0xC1900101 – 0x40021.

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Method 1: Clean up the Disk

A full hard drive can also cause the “installation error 0xC1900101 – 0x40021” issue. Thus, you should clean up the hard drive, which can help your PC get great performance. You can follow the steps below to clean up your hard drive:

1. Type disk cleanup in the Search box and choose Disk Clean-up from the best match.

2. In the pop-up window, the system drive is selected by default. You need to click OK to continue.

3. Then, you will see how much disk space you can get in total by deleting all files listed in the box.

4. Now, check the files that you want to delete and click the OK button.

5. Now, you need to click Delete Files to confirm that you want to permanently delete these files.

Method 2: Update the Graphic Driver

You can also choose to update the graphic driver to fix the Windows 11 installation error code 0xC1900101 – 0x40021.

1. Press the Windows + R keys to open the Run box and type devmgmt.msc. Then press Enter to go to Device Manager.

2. Double-click Display adapters to expand it. Then right-click your graphics card driver and choose Update driver.

3. Then, you should choose Search automatically for updated driver software and then follow the instructions to complete the process.

Method 3: Run Windows Update Troubleshooter

You can try to run the Windows Update troubleshooter to fix the “Windows 11 installation error 0xC1900101 – 0x40021” issue. Here’s a tutorial.

1. Press Windows + I to open the Settings application.

2. Go to System > click Troubleshoot.

3. Click Other troubleshooters to expand all troubleshooters, and then click Run next to the Windows Update section. 

Method 4: Run SFC

The presence of corrupt/damaged system files in Windows may also lead to the installation error 0xC1900101 – 0x40021. To repair them, you should try the System File Checker.

1. Type cmd in the Search box, and then right-click the Command Prompt app and select Run as administrator.

2. Type sfc /scannow command in the elevated command prompt. This process may take you much time to scan, please wait patiently.

Method 5: Repair Install Windows

If the above methods are not working, you can upgrade to Windows 11 22H2 via ISO file and download the latest updates to remove the Windows 11 installation error 0xC1900101 – 0x40021. Here are the steps:

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1. Go to the Windows 11 Download page.

2. Under the Download Windows 11 Disk Image (ISO) part, click the drop-down menu to choose Windows 11 (multi-edition ISO) and click Download.

3. Then, you need to choose a language by clicking the drop-down menu. After choosing it, click the Download button.

4. Next, click the 64-bit Download button to start the downloading process.

5. When the file has been downloaded, right-click it and select Mount from the context menu.

6. Choose the mounted drive and then double-click the Setup file option to begin the installation.

7. Then, click the Not right now button. Navigate to Next > Accept. During the process, select all the items you want to keep.

8. Finally, click the Install button and wait for the process to complete.

9. Then, go to download and install the update again.

Final Words

In conclusion, this post has introduced several useful methods to fix the Windows 11 installation error 0xC1900101 – 0x40021. If the error code occurs, try these methods.