<There are dozens of other machines like that. The Xerox Daybreak I have <here has a similar setup. The TRS-80 Model 4 I have has a hard disk box <containing a WD controller card and an ST506 hard disk. That one would be <easier to modify to use a different disk, but still not trivial. the problem is often more than just having a formatter program or even the capability. Many systems the OS may have built in limitations on what drives may be used. CPM typically the bios is set up for only one trivel geometry and changing it is a assembly language project if your lucky enough to have sources. Allison