Hi, it sounds as if the disks either
1) are not formatted for the amiga
or
2) are not bootable disks (ie they are designed to run through the workbench).
Are there any original amiga disks with the computer, for example any which say 'workbench' on them?
It is always possible the disks are bad - they are, after all, over a decade old. Especially copied disks will deteriorate in that time.