I successfully installed a 3 1/2" ST-506/412 drive (a Seagate, IIRC), which worked OK. Has to be 3 1/2" because it fits in the floppy bay. You have to find a controller card which has the power output because the floppies take power off the drive cable. I think you could bodge it to take a hardcard in one of the expansion slots. manney The Model 25 takes the cake for the world's most stupidly designed PC -- and the hardest to work on.