When you say you've taken "an image" - is than as in a single exposure? Coz if so, it's not technically going to be a true HDR. Not that I'm knocking it, most of my "HDR style" images have been pseudo HDRs done from a single shot.
I've tried just about every HDR program there is, and I'd say Photomatix is definitely the one to go for. Though I did try another one (can't remember the name now) and it had lots of weird effects, not realistic but certainly interesting!