HDR software for beginner

Hi All,

In one of my last threads (on photographing stary night skies) I got a suggestion from Erikka to use HDR technique to get brighter stars using a 15 sec exposure.
Though I am aware of HDR technique, I have never tried it till now. I understand that shooting with different exposures is one part of the creating a HDR and using a HDR software to merge them is the other. I do not have any software that can be used to merge the different exposure shots to create one single shot. I normally use Picasa or Lightroom 2 (occasionally) to edit my pictures.

I gave a search of DPREVIEW site and found around 5 HDR software. However, all need to be licensed.

Is there any HDR software that is free like Picasa?

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--Rinjo