New HD disks not working in 1541?

Hi, now that I have my old C64 setup back I found that I could not format newer 5.25" HD disks on the 1541 or 1571. It just bumps and blinks and stops. Does the 1541 require hard sectored disk? I don't think so, because I can still remember today that my first disk ever said "BASF Flexi Disk, 5.25", Singled Side, Double Density, Soft Sector." So what's the trick to get media working? Bulk eraser? (BTW: It's been over 15 years and I still have that disk and could actually read one side of it, that's fun!) thanks -Gunther -- Gunther Schadow, M.D., Ph.D. gschadow(a)regenstrief.org Medical Information Scientist Regenstrief Institute for Health Care Adjunct Assistant Professor Indiana University School of Medicine tel:1(317)630-7960 http://aurora.regenstrief.org