If you've recently installed or partitioned an existing hard disk in Ubuntu Linux, you will need to format to a file extension that you can use in Ubuntu, such as ext3 or fat32. Ubuntu comes with built-in disk formatting tools that can be run from the command line.
Open a Terminal command line under Applications > Accessories. Type "sudo fdisk -l" followed by "Enter." This displays information on all of your installed hard disks. Locate the new hard disk and write down its name, i.e. "dev/sdb1." You can identify the new disk by its classification under "System." If it does not say "Linux," it is not yet formatted.
Type "sudo mkfs -t ext3 /dev/sdb1" (replacing "dev/sdb1" with the name of your hard disk that you wrote down in Step 1) and press "Enter." This is to format your system to ext3. For fat32, see Step 3.
Type "sudo mkfs -t fat32 /dev/sdb1" (replacing "dev/sdb1" with the name of your hard disk that you wrote down in Step 1) into the Terminal and press "Enter." This formats the hard disk to fat32.