Symptoms

During the Ubuntu installation or Starting the Ubuntu, the following error appears: 

Ubuntu error:
Installing, this may take a few minutes...
WslRegisterDistribution failed with error: 0x800700b7
The distribution installation has become corrupted.
Please select Reset from App Settings or uninstall and reinstall the app.
Error: 0x800700b7 Cannot create a file when that file already exists.

Cause

There are several main reasons why the following error might appear: 

• Disabled Service
• Missing Distributions
• Some Ubuntu Distributions files are missing

Resolution

Disabled Service

Firstly, you need to check whether it's an issue with the service and whether it is started:

Try to restart the LxssManager Service and test it:

 
Or via CLI:

sc query LxssManager
sc stop LxssManager
sc start LxssManager

If the following Service is missing you can install it:

1. Type in the following command and press enter.

   lxrun /install

   Note: Try running this command in Powershell if it doesn’t work in Command Prompt.

2. This will trigger the download from the Microsoft Store, press “Y” to initiate the downloading process if asked by the command prompt.
3. Check to see if the issue persists.
   Note: This command can also be executed on the PowerShell (Administrator). But if it isn’t recognized, or the service has been restarted and running at the moment, and you still face the problem, the Ubuntu dist is missing or corrupted. So let's move to the second resolution.

Missing Distributions, Ubuntu files, or corruption 

Please perform the instructions from the article below:
TL - Resolution of any Ubuntu error (or most of them that are related to WSL/Ubuntu installation)