Hi Daniël,
To easily address your concern, I’ve merged your posts here at the Non-Hotmail Questions (Referral) forum.
I’ve checked both Hotmail accounts that you’ve provided and verified that the mailbox associated with them are inexistent from our server. This is the reason why you’re unable to reset the password for either accounts. However, since you’re also being prompted that the Live.com e-mail address is already in use when trying to sign it up, I recommend that you get in touch with the Windows Live Technical Support Team. To contact their team, follow the steps below:
1. Go to https://support.live.com/default.aspx?productkey=wlid
2. Select one of the help topics displayed on the left panel.
3. Click Get more help at the lower-right corner of the window then click Get support.
4. Complete the e-form and then click Submit.