Boot sector question

I have a floppy disk that boots MS-DOS and executes some commands.

The last command I want it to run is something that loads the hard disk boot sector in and jumps to it, thus relinquishing control from DOS.

My code is:

mov ax, 201h
mov bx, 7c00h
xor cx, cx
mov es, cx
inc cx
mov dx, 80h
int 13h
jmp 0:7c00h
but this just hangs. Any ideas what could be going wrong?

Check cf/ah for the status/return code. How many hard drives do you have? Perhaps the first disk is a GUID Partition Table disk?