I suspect that the laptop may be sending spam out in the background.
Run a full scan with malwarebytes: https://www.malwarebytes.org/free/
You will likely need to run it more than once to get everything.
Also follow up by running adwcleaner: http://www.bleepingcomputer.com/download/adwcleaner/
And also with Junkware Removal Tool (JRT): http://thisisudax.org/?p=1
If you do not have antivirus software, you need it. Microsoft Security Essentials, Avast, or AVG are free options. Run a full scan with one of these as well.