I've normally written my own whenever I needed to look at sector 0. Use a 16-bit compiler in DOS and you won't go wrong. You can get Turbo C++ from the Borland museum

Software Interrupt 13H
Read a diskette sector
AH=02H
AL=number of sectors
CH=track
CL=sector
DH=head
DL=drive (1=a, 2=b)
ES:BX = pointer to buffer

Result CF=success/failure
AL=status
AH=sectors read

Reading hard disks
AH=0AH
the rest of the registers are the same

Have fun.