Yes, it must be something common to what hasn't been replaced, e.g.:

a) if a HD data or power cable is bad the disk will fail POST and
   you'll never get as far as booting from floppy, or

b) if the +12V supply is bad it may not affect the mobo much but
   the disks won't be happy.

Steven J. Wolfe said:
>
>Have you replaced the cable for the Hard Drives! One of the cables may have
>a bad connection. Also you may want to check the Voltage of the Power
>Supply, or try with a known good supply.
>
>Robert Prickett said:
>>
>> Decided to switch on a trusty 486/DX100 and got this:
>> Disk I/O error-replace the disk
>><snip>
>> Disk I/O error
>> replaced hard drive
>> Disk I/O error
>> replaced floppy drive and tried to boot from there
>> Disk I/O error
>> <snip>
>> There's nothing left except the box itself, mouse, and KB
>><snip> I don't have anything left to replace...?

Len Warner <[log in to unmask]> WWW Pager http://wwp.mirabilis.com/10120933