It should boot from a floppy if it's in there first..
But you can temporarily disable the HD.
Power up the 1200 holding BOTH mouse buttons down.
You will get a boot menu, and you can choose to disable the HD there.
(It's not battery backed up or flash, so that change is for that power cycle only.)
desiv
Nah, if Workbench has loaded just pop the disk in and do a reset and it will boot from the disk if it is bootable, if not it will boot to workbench again from the harddrive.