Some hints:
- You should load
CH
with zero, not one, beause cylinders are numbered from zero. - Upon failure an error code is returned in
AH
, have you looked at that? - Booting from cd (iso as you say) complicates things, in particular check if you have floppy emulation enabled. Or just use a virtual floppy until you get things right.
- The BIOS usually passes the boot drive for you in
DL
so there should be no need to overwrite that.
Using floppy image and fixing point #1, it works for me with bochs and qemu (don't have virtualbox).