If you just need access to the previews, try this: http://regex.info/blog/lightroom-goodies/preview-extraction
If you actually need help building it, let me know and I'll move this to the SDK subforum where you may get a little more assistance on that.
I think he is looking for C/Java code, not a script/plugin.
In any case, anybody looking to recover previews should be aware that most plugins or external apps DO NOT assign a proper ICC profile to the extracted previews. The extracted previews are *usually*, meaning NOT ALWAYS AdobeRGB, but untagged: will be interpreted as sRGB. Yeah, that's why they will look different than the original.
I don't know about JF's plugin.
(Adobe's recovery script does NOT handle ICC profiles correctly).
PreviewExporter is the only plugin I know of that handles ICC profiles properly - if anybody knows how JF's plugin handles ICC profiles - do tell.
Note: PreviewExporter includes source code - it should be straight-forward to translate to C/Java.
Victoria, I actually need help building it. I need either a code sample, or some type of SDK documentation - anything I could use to build an app from scratch.