Have Superuser, but still cannot tether

[m124]

I have a HTC Evo 4G (Android version 2.3.3) and followed the instructions for rooting. In the end I do have a Superuser app, but when I try to tether with the Wireless Tether app, it says it cannot start tethering and is asking me if I rooted.

How do I figure out if I am rooted or not?

TIA