Bit of confusion here, perhaps. Topaz is not HDR software. It has some great effects - and I'm active on the Flickr Topaz Software Group testing various settings for different effects. But it's not HDR.
HDR (High Dynamic Range) photography is, in its simplest form, a method of taking two or more identical shots except that they have different exposures, to take account of different amounts of light in different parts of the view. For example, a normal single photograph would find it very difficult to capture details inside a room and, simultaneously, the view through the window - the light levels are just too far apart for them both to be captured in one exposure.
Make two exposures (or three or more - some people use nine) all of the same basic view, (you'll need a tripod) but at different exposures (in fact, different shutter speeds, as changing the aperture would do some very odd things with the Depth of Field). Most modern DSLRs give you bracketing options, mostly giving three or five shots that are between 1/3rd of a stop to 2 stops apart.
HDR software, like Photomatix, Dynamic HDR and a few others (which all seem to have trial versions), combines the images, finds the best details from each exposure and puts them all together. Contrast is lost to a large degree but some interesting results can be obtained. However, at this stage, the combined picture has such a High Dynamic Range that it cannot be viewed on a normal computer, so the software has to do some calculations to put light levels into order so that it can be viewed - this part is called tone mapping.
Some people go nuts with the tone mapping, producing some of the ugliest shots you could imagine, with halos around contrasting edges and a generally 'cartoon-like' look. There are HDR groups on Flickr where "anything goes" and there are others that only allow realistic or true-tone images. Used with subtlety, HDR is excellent..... I know of some Real Estate Agents who take pictures with HDR so that they can include all the shady areas of a room and a view of the garden outside!
The software can also make "pseudo" HDR, using just one jpg and stretching it all over the place. However, if the jpg hasn't got details in all the areas in the first place, you can see that this is not a great idea. The trouble is, it will still tone-map the combined shot and to many people it will look, at first, like an HDR.
You can, to some extent, make your own HDR - multiple raw shots at different exposures can be combined with layers and layer masks in Photoshop and Elements - and you won't get odd artifacts - but it's a bit complicated. You could also make different versions via Adobe Camera Raw to get different exposure effects and make three or more versions of a single raw, then combine them as above. But a single exposure will not capture anything like the dynamic light range of lots of shots using different EVs.