Tagz. In answer to your question how to do multiple raw conversions of the SAME image....
The easiest way to do it is to use Russell Brown's little tool, Place-A-Matic. here is a tutorial on how to use it http://av.adobe.com/russellbrown/MergeAndPlaceSM.mov The tutorial contains 2 of his tools. Merge-A-Matic and Place-A-Matic. Place-A-Matic is the one you want and is in the second part of the tutorial. The actual Place-A-Matic tool can be downloaded (for free) from http://www.russellbrown.com/tips_tech.html Just scroll down that page a bit until you come to Dr. Browns' Services 1.4. There you will see the Easy Installer (Windows and Mac versions.
Essentially, what Place-A-Matic does is create workspace in CS2 (btw, all of the above presupposes you have Photoshop CS2??). Open your image in Adobe Camera Raw. You can then edit that image and then place it in CS2, it will then take you back into ACR where you can do another raw edit of that same image. When you've completed that it will place that in CS2 as well. So what you have is two differently converted Layers sitting in CS2 which you can then merge, typically with Layer Masks. If you aren't happy with how you have done the raw conversion of one (or both) of them, you can click on the Layer and it will take you back into ACR for you to re-edit. It can do this because it places them in CS2 as Smart Objects.
All of he above can be done fairly easily without Place-A-Matic but the tool just makes life really easy.
This is not HDR though... but a kind of pseudo version.... but, it works very well. HTH