mount -t msdosfs /dev/ad2s1 /mnt/windows

 [root@fbsd1 /mnt/windows 19:58:37] #  fdisk /dev/ad2
******* Working on device /dev/ad2 *******
parameters extracted from in-core disklabel are:
cylinders=77504 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=77504 heads=16 sectors/track=63 (1008 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 12 (0x0c),(DOS or Windows 95 with 32 bit FAT (LBA))
    start 63, size 20487537 (10003 Meg), flag 80 (active)
        beg: cyl 0/ head 1/ sector 1;
        end: cyl 1023/ head 239/ sector 63
The data for partition 2 is:
sysid 15 (0x0f),(Extended DOS (LBA))
    start 20487600, size 57607200 (28128 Meg), flag 0
        beg: cyl 1023/ head 239/ sector 63;
        end: cyl 1023/ head 239/ sector 63
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
 [root@fbsd1 /mnt/windows 20:04:41] #

mkdir /mnt/windows/c_drive
mkdir /mnt/windows/d_drive
mount -t msdosfs /dev/ad2s1 /mnt/windows/c_drive
mount -t msdosfs /dev/ad2s2 /mnt/windows/d_drive