Hi, see if the info in this Windows Live link helps
It's possible the machine is infected, but also possible the address has been harvested and is being spoofed, or that the account has been hacked in which case...followup with Windows Live help is recommended.
If you think the machine is infected:
Please follow our pre-posting process outlined here:
After running through all
the steps, please post the requested logs in the Virus/Trojan/Spyware Help
forum, not here.
If you have trouble with one of the steps, simply move on to the next one, and make note of it in your reply.
Please note that the Virus/Trojan/Spyware Help forum is extremely busy, and it may take a while to receive a reply.