How do I nuke compatibility mode in my registry?

I just built a machine w/o a floppy disk. However, win'98SE device manager says that drive:a is using dos compatibility mode file structure.

I've turned off the search for floppy options under file system, and I've even turn off the fdc in my bios. Still says that same BS about my drive a: (which doesn't even exist).

There's a key in the registry that I need to nuke, but I can't remember what. Ideas?

Thanks,

Brian H.