They aren't, specifically, targeting you. They just have a program that works to break passwords on email accounts. If this were the one you regularly use you would notice right away, but since this is an old email address you may never notice that things are being sent out in your name.
The best way to prevent this is to close your old email accounts. Here are links to close your account for the more popular email providers. If your provider isn't on the list contact them for help.
Google:
http://support.google.com/accounts/bin/answer.py?hl=en&answer=61177
Yahoo:
http://help.yahoo.com/kb/index?locale=en_US&y=PROD_ACCT&page=content&id=SLN2044
AOL:
http://help.aol.com/help/microsites/search.do?cmd=displayKC&doc&externalId=217428
Hotmail: http://windows.microsoft.com/en-US/windows-live/account-close-account