How to choose a username when using a Microsoft Account in Windows 8?

As noted in my other question, Windows assigns a strange username (<login>_000) when logging in with a Microsoft Account to a computer for the first time. It is quite difficult to change this username (and associated folder in C:\Users) later.

Is it possible to choose the username during the first logging in with a Microsoft Account?

One way to do this (not very convenient, but works) is to create a local account with a desired username and then immediately connect it to a Microsoft Account.

To do this:

1. Go to Charms Bar -> Settings -> Change PC Settings -> Users -> Add a user
2. Choose Sign in without a Microsoft Account at the bottom of the wizard
3. Choose Local account
4. Enter your desired username in the Username field (leave password blank)
5. Press Next and then Finish
6. Switch current user to the newly created one (in the upper-right corner of the Start Screen)
7. Enter the Users settings exactly as in step 1.
8. Click Switch to a Microsoft Account
9. Enter your Microsoft Account e-mail and press Next
10. Complete the wizard (enter your password, fill in security info, etc.)

You'll then have a Microsoft Account with a chosen username.

You are asking the wrong question- you should be asking is it possible to create a user account before logging in with your Microsoft account. Yes it is possible- I don't know the exact steps, however, disabling your wifi, of unplugging your ethernet cable should leave you with no other choice than to create a local account which you would later connect to a Microsoft account, as you pointed out in your answer.