This method is not perfect but you can extract some files from the dat file.
1. Download Offset file unzipper 0.3.3 from
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2. Open offzip in CMD
3. Issue command, offzip -a datfile outputdir 0
Example: offzip 5_Effect.dat effect 0
4. Under the outputdir, lots of dat files will be generated
5. These smaller dat files are actual files such as kfm, nif, kf, dds, xml, etc.
6. Rename them to their actual extension.