KrZ

i think it is more likely that your personal machine has some kind of computer virus that hijacked your hotmail when you login and obtained your account information. keep your machine update with all the security patches and make sure your anti virus software is up to date. and don't download softwares from third party sources or warz stuff.
This is nothing new, if you check a lot of your junk mails, there are a lot of legit email addresses being used without the owner of the address even knowing it, you usually find out when you get a email bounce message. Another thing is, i always have an email address only used for register with different kind of services. Dispite all the effort you put in to tick the box "not to share your detail with third parties " when you register to a site or a service, your email address always ends up at some wrong hand, which they use to send junk email with.