Windows Vista introduces a Preview pane in folder view, using which you can preview image and text files, and play multimedia files from the Preview pane.

The PreviewConfig application will allow you to add or remove preview handler for a file type. For instance, you can add a plain-text Preview handler for a file type that contains text. Here are some examples:

.REG, .VBS, .CPP, .VB, .CS, .CSS, .BAT, .CMD

PreviewConfig utility registers the handler on the ProgID. If a ProgID does not exist
for the said file type, it registers the hander on the file type itself.