No. NEF files (7.8MB on a D1x) are larger because they store the original 12-bit camera sensor data in an essentially uncompressed form. JPEG files (~2MB on a D1x at full resolution) are substantially smaller because the camera stores the data as 8 bits and compresses it further. Lower resolutions are only available in JPEG, and create smaller files.
The same will be true on a D100, though until we get cameras, we can't know the exact file sizes.
Thom Hogan author, Nikon Field Guide author, Nikon Flash Guide author, Complete Guides to the N65, N80, and F100 author, Complete Guide to the Nikon D1, D1h, & D1x www.bythom.com
Thom Hogan author, Nikon Field Guide and Nikon Flash Guide author, Complete Guides to most Nikon cameras www.bythom.com