Hotmail message – It looks like someone else might be using your account

Good Evening,

We are in need of some serious help please. My wife is having serious problems accessing her hotmail account.

When ever she try's to log on she gets the following message "It looks like someone else might be using your account".

We can't provide all the answers being asked by  the microsoft web-site so we can't unlock the account.

She remembers a security alert at work a few months back and suspects her details have been compromised and her account has been hacked.

The back-up e-mail is no longer active so she can't even receive a new password e-mail.

Her e-mail address is *** Email address is removed for privacy ***. She is really beside herself with worry, any advise / guidance would be great.

Thanks in advance

Anthony