repartition external hard drive

i purchased a western digital 160 GB hard drive,
installed it into an external enclosure to convert to
firwire connection.

the tech support at the store installed the drive and
formatted it to fat32 as a single partition.

i want to partition the drive to 2 partitions of 80 GB
each. according to microsoft knowlege base, (Microsoft
Knowledge Base Article - 255867) i should open the
command box and type FDISK to do this. when i do this i
get the error message: FDISK is not recogized as an
internal or external command, operable program or batch
file.

how do i enable fdisk, or more importantly, how do i
partition this external drive into two 80GB drives?

thanks in advance