Most likely you used either an old version of FDISK or forgot to select Yes
to large drives when asked. Thus the partition was generated using FAT16
which is limited to about 2G.

You could use Fdisk and generate an extended dos partition and then generate
logic drives within the extended partition.

If you want to increase the size of the existing primary partition (which is
about 2G) then your options are:

1. Use Fdisk to delete the present partition. Reboot and use fdisk to
generate new partition. This would result in loss of all data in the
existing partition.

2. Use a third party application such as partition or bootitng to change the
existing partition without loss of data.