Windows 7 or Linux Depending on which computer you received it came with either Windows 7 or no operating system at all. This happened because some of the older systems...
On September 10th, 2014 5 million Gmail passwords were leaked on a Russian bitcoin forum. It would be a good idea to check if your account info was possibly leaked. To check go to securityalert.knowem.com.
If you need to change your password check out this Lifehacker article to learn how to create a strong password.
UPDATE: The original site that I linked to above has come under some scrutiny. I have changed the link to a password checker from a trusted company. The original site isleaked.com is most likely safe as I tried it myself before posting this article and noticed no strange activity. Better to be safe though.