Use a bit copy program to get a copy of the original disk. Now with a disk editor look at: track $00 sector $06 byte $11 change $D0 $F7 - BNE to $EA $EA - NOP NOP byte $2E change $D0 $F7 - BNE to $EA $EA - NOP NOP sector $0F byte $08 change $D0 $F7 - BNE to $EA $EA - NOP NOP This allow the check routine to fail with no harm.