dcraw is a free, open source program to process raw image files, including those from most of the early Kodak DSLR's. I've had great success converting TIFF files from a DCS 420 using this program.
Supported Kodak DSLR's: DCS200, DCS315C, DCS330C, DCS420, DCS460, DCS460A, DCS520C, DCS560C, DCS620C, DCS620X, DCS660C, DCS660M, DCS720X, DCS760C, DCS760M, EOSDCS1, EOSDCS3B, NC2000F, Kodak ProBack, PB645C, PB645H, PB645M, DCS Pro 14n, DCS Pro 14nx, DCS Pro SLR/c, DCS Pro SLR/n
The program home page is found at http://www.cybercom.net/~dcoffin/dcraw/
You can download and compile the C source code yourself, or download an executable version from the program home page or some other site. Alternatively: Google "dcraw executable" or something similar.
You'll need to read the documentation on how to use the (command line) program, but to convert a single file you can do something like this:
c:\dcraw.exe -T c:\test\DCS00750.tif
..where c:\dcraw.exe is the path to the program executable, -T means that you want the converted file to be in a standard TIFF format (the default is .ppm - portable pixmap file format), and c:\test\DCS00750.tif is the path to the file you want to convert.
Just write dcraw and press enter to see a list of available switches. Like this:
For more tips and examples you can search Google for "dcraw usage", or something similar. You can also take a look at this Wikipedia article: http://en.wikipedia.org/wiki/Dcraw
Another one: http://www.outbackphoto.com/artofraw/raw_07/essay.html
If you didn't understand anything of the above, you can take a look at this simple-to-use Windows program instead:
http://www.nikonweb.com/DCS_convert/
Jarle