How did I get a virus on my other computer?

[Belie]

You (or your husband) downloaded something or clicked on a website and you did not have good enough protection.
No, you did not get it from Cafe World or Farmville.
No, you would not have gotten it from a store-bought game.

Likely places you can get viruses are from your email (by clicking on the attachments sent from spam), from spammers on Facebook (by clicking on the false links they send), from porn websites, and from programs you downloaded to the computer (particularly illegal movies or music).
Anytime you download anything to your computer you should always scan it for viruses before you open it. If you do not already have virus protection, then download Avast! It's free and safe.
Don't go to unknown websites, even if they're linked to by friends, especially if they have a tiny or otherwise odd-looking URL.