If you have the win98 disk, look in the folder /win98/cabs (I think, it's been so long since I screwed with 98). It should be in that folder, or compressed in one of the .cab files. I have reserected a few blown OS's by doing this (though not the rundll32 file).
Chris, If I'm not mistaken, the rundll32 file is the file that runs the dlls, but I don't think it changes over time. The registry changes all the time and that's what points all those dlls to the rundll handler. But it is 98, and we all know the legendary stability of 98.
Point is, if restoring the file makes it boot, cool, boot it, back you stuff up and reload a clean OS. Frankensteining an OS is a bad idea, and should only be a temporary fix to save data.
Next week: How to retrieve data from an NTFS disk when the OS is hosed!!!
Whitt....