D:\...>sfdx force:org:list
    === Orgs
         ALIAS         USERNAME                                    ORG ID              CONNECTED STATUS
    ───  ────────────  ──────────────────────────────────────────  ──────────────────  ────────────────
         DevHub        daniel.ballinger+[email protected]           00D7F0000000001AAA  invalid_grant

I just had my trial Dev Hub org expire (invalid_grant), so I created a new Dev Hub and registered it with `sfdx force:auth:web:login -d`.

That moved the `(D)` marker to my new dev hub, but the old one was still hanging around. [Peter's solution][1] would have worked, but I thought I'd try a `sfdx force:org:delete -u DevHub` to see what happens now the old org is no longer the nominated dev hub.

    D:\...>sfdx force:org:delete -u DevHub
    Enqueue scratch org with name: DevHub for deletion?  Are you sure (y/n)?: y
    Successfully deleted scratch org DevHub.

Appears to have worked even though it isn't a scratch org. The old dev hub org no longer appears for a `sfdx force:org:list`

  [1]: https://salesforce.stackexchange.com/a/181781/102