Non-www presents some challenges out of the box. We've discussed them here in great detail over the years. I even made the decision to strip my WWW a while back and after a lengthy topic on the Pros and Cons, I changed my mind again. :)
No More WWW
[webmasterworld.com...]
In your case, depending on how long it has been that way and what percentage of your inbound links are linking without the www will determine how you move forward with the promotion of your domain.
How do other pages within your site respond? Like this...
example.com/folder/
Or like this...
folder.example.com/
