[root@localhost ~]# fdisk /dev/sdb 

Command (m for help): p

Disk /dev/sdb: 4040 MB, 4040724480 bytes
125 heads, 62 sectors/track, 1018 cylinders
Units = cylinders of 7750 * 512 = 3968000 bytes
Disk identifier: 0x6f20736b

This doesn't look like a partition table
Probably you selected the wrong device.

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   ?      100405      247697   570754815+  72  Unknown
Partition 1 has different physical/logical beginnings (non-Linux?):
     phys=(357, 116, 40) logical=(100404, 79, 11)
Partition 1 has different physical/logical endings:
     phys=(357, 32, 45) logical=(247696, 24, 51)
Partition 1 does not end on cylinder boundary.
/dev/sdb2   ?       21767      271577   968014120   65  Novell Netware 386
Partition 2 has different physical/logical beginnings (non-Linux?):
     phys=(288, 115, 43) logical=(21766, 48, 47)
Partition 2 has different physical/logical endings:
     phys=(367, 114, 50) logical=(271576, 60, 42)
Partition 2 does not end on cylinder boundary.
/dev/sdb3   ?      241276      491086   968014096   79  Unknown
Partition 3 has different physical/logical beginnings (non-Linux?):
     phys=(366, 32, 33) logical=(241275, 3, 30)
Partition 3 has different physical/logical endings:
     phys=(357, 32, 43) logical=(491085, 14, 39)
Partition 3 does not end on cylinder boundary.
/dev/sdb4   ?      372346      372354       27749+   d  Unknown
Partition 4 has different physical/logical beginnings (non-Linux?):
     phys=(372, 97, 50) logical=(372345, 119, 25)
Partition 4 has different physical/logical endings:
     phys=(0, 10, 0) logical=(372353, 14, 33)
Partition 4 does not end on cylinder boundary.

Partition table entries are not in disk order

Command (m for help): d
No partition is defined yet!

Command (m for help): p

Disk /dev/sdb: 4040 MB, 4040724480 bytes
125 heads, 62 sectors/track, 1018 cylinders
Units = cylinders of 7750 * 512 = 3968000 bytes
Disk identifier: 0x6f20736b

   Device Boot      Start         End      Blocks   Id  System


Command (m for help): v
7892039 unallocated sectors

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

[root@localhost chinmay]# mkfs -V -t ext3 /dev/sdb 
mkfs (util-linux-ng 2.14.1)
mkfs.ext3 /dev/sdb 
mke2fs 1.41.4 (27-Jan-2009)
/dev/sdb is entire device, not just one partition!
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
247008 inodes, 986505 blocks
49325 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1010827264
31 block groups
32768 blocks per group, 32768 fragments per group
7968 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736

Writing inode tables: done                            
Creating journal (16384 blocks):