I'm sorry you're having trouble with the 1st gen! :disapprove: the Rockbox site has a list of (known) compatible drives:

http://www.rockbox.org/wiki/HardDriveReplacement

I think I read somewhere the first gen iPods couldn't take anything larger than 10GB but don't quote me on that.

And just in case you have some CompactFlash cards lying around this might be worth a shot: http://www.rockbox.org/wiki/CFModGuide

Good luck!