For a SE to run SuperDrives, you need the FDHD ROM upgrade (similarly, for a II you need the Mac II SuperDrive upgrade, which is a set of IIx ROMs). SEs make a nice bridge system, though, set them up with an 800k drive, network, and a version of System 6 and they are good for writing out 400k floppies. System 7 had issues with MFS (400k floppy filesystem).