HP 2566C - Manual (Page 26)

Remove the upper ribbon spool from the retainer cups. Throw away
the used ribbon (Figure 3-6).
6. Discard the old ribbon.
Replacing the Ribbon
When you replace a ribbon, the ribbon spools must be mounted correctly
so they wind in the right direction (Figure 3-7). If the ribbon is on
backwards it will not function properly. Also, make sure that both spools
fit solidly into the drive hubs (rotate the spool until it snaps onto the
drive hubs). If it does not fit correctly, the ribbon spool will be broken
by the drive hub.
PREPARING THE PRINTER FOR OPERATION 3-5