Load DEBUG from DOS and enter the following command(s) at the "-" prompt:
                -D 40:0 L E    (NOT case sensitive)
           It will display the following information:

                0040:0000  F8 03   F8 02   E8 03   E802   -   78 03   78 02   BC 03

             This means:  COM   COM   COM   COM       LPT     LPT    LPT
                                        1           2           3            4              1           2        3

                Interrupt:      4           3            4           3              7          5         -
 

                The above shows all of the devices in use (unlikely), so the line could look something like:

                0049:0000  F8 03   00 00   00 00   0000   -    78 03   00 00   00 00

                                    COM                                              LPT
                                       1                                                      1

                This would be a more realistic view of what you would see... this is also a quick & dirty way
                to see what your BIOS thinks is in use.  Remember that these pairs are shown in reverse
                of the way we read them, so  F8 03 is really  3F8
                                                                                                                                                -Ted Mieske
 
 

        Here is another approach that won't touch the MBR; it just zero's out the drive. This is equivalent to a drive from the Factory:
                Load DEBUG from DOS and enter the following command(s) at the "-" prompt:
        (NOT case sensitive)

            -A CS:100  <enter>
            xxxx:0100   MOV AX,330      <enter>
           xxxx:0103    MOV CX,1        <enter>
           xxxx:0106    MOV DX,80     <enter>
           xxxx:0109    MOV BX,3800  <enter>
           xxxx:010C   MOV ES,BX      <enter>
           xxxx:010E   INT 13               <enter>
           xxxx:0110   INT 3                  <enter>
           xxxx:0111   <enter>
             -G  <enter>
             -Q  <enter>
                                                                                                                                              - unknown

            (NOT case sensitive)

              -A CS:100   <enter>
           xxxx:0100     MOV   AX,301  <enter>
           xxxx:0103     MOV   BX,200  <enter>
           xxxx:0106     MOV   CX,1     <enter>
           xxxx:0109     MOV   DX,80   <enter>     ( 80=hd0   81=hd1   etc.)
           xxxx:010C     INT     13  <enter>
           xxxx:010E     INT     20  <enter>
           xxxx:0110     <enter>
                -G  <enter>
                -Q  <enter>
.
                Program should terminate normally.  If it DOES NOT, you entered something WRONG!
             NOTE: This will REMOVE all information from the Boot Record!!

             I have used this many times when a High-Level format would not work, or running FDISK or FDISK /MBR won't work!
            I know your told NOT to do this, but I have never had a problem with this trick when a drive just WON'T configure.

                                                                                                                                                - Ted Mieske