Thanks for that , AP.
I assume that you've taken your images in jpeg format, since (according to what I've read) that requires several exposures. However, as I read it, taking a single photograph using the RAW format allows you to extract the different images from the one file with apparently different exposures, which can then be used to produce HDR photos. I like that idea because, for example, you could produce an HDR picture from an 'action' shot (such as a high jumper leaping over the bar).
Annoyingly, while I know that I've read a (print) article on the subject, I can't remember where it was. It must have been in one of the many magazines which are cluttering up my living room, so I'll have to delve deep into the piles of rubbish which currently surround me in order to find it ;-)
Chris