simple

type a ; infron of setpatch in your s-s , then try again to start the system.
if it still doesnt, just try and mount cd as normal from cli like this:
assign env: ram:
assign t: ram:
mount cd0:
os3.9 should then be readable.
make sure you mount the unit u are supposed to,
to check that , go to devs:dosdrivers/
and list that dir.
incase u meet probs let me know r use this thread as you aint in deepshit just yet.
cheers
pps:reason is prbably as stated earlier you got an way old setpach installed..