Create a Hello World Lightning Web Component

When I run this code with a different name (helloworld), it worked at first, but now it gives me an error like this.

20:01:37.571 Starting SFDX: Create Lightning Web Component

target dir = d:\salesforce\HelloWorldLightningWebComponent\force-app\main\default\lwc

   create d:\salesforce\HelloWorldLightningWebComponent\force-app\main\default\lwc\helloWorld\helloWorld.js

   create d:\salesforce\HelloWorldLightningWebComponent\force-app\main\default\lwc\helloWorld\helloWorld.html

   create d:\salesforce\HelloWorldLightningWebComponent\force-app\main\default\lwc\helloWorld\helloWorld.js-meta.xml

20:01:37.940 Finished SFDX: Create Lightning Web Component

20:03:06.931 Starting SFDX: Deploy Source to Org

=== Deploy Errors

PROJECT PATH  ERRORS                                                                        

────────────  ──────────────────────────────────────────────────────────────────────────────

              duplicate value found: <unknown> duplicates value on record with id: <unknown>

              Cannot find Lightning Component Bundle helloWorld.                            

              Cannot find Lightning Component Bundle helloWorld.                            

20:03:10.844 ended SFDX: Deploy Source to Org@