Its quite easy. You must simple load the executable into memory using BIOS calls as follows.
mov ah, 02h
mov al, 01h
mov ch, 0h
mov cl, 2h
mov dh, 0h
mov dl, 1h
mov bx, 1000h
int 13h
This will load the second sector from the disk and place it at memory possition 1000h. There is no error...