whenever i am running some comands , it displays error message

[root@ftp Delhi]# fdisk -l
-bash: /sbin/fdisk: Input/output error

[root@ftp Delhi]# last
-bash: /usr/bin/last: Input/output error

[root@ftp Delhi]# ls
01Dec2006 05Dec2006 09Nov2006 14Nov2006.test 20Nov2006 27Nov2006
02Dec2006 05Nov2006 10Nov2006 15Nov2006 21Nov2006 28Nov2006
02Nov2006 06Dec2006 11Nov2006 15Nov2006.test 22Nov2006 29Nov2006
03Dec2006 06Nov2006 12Nov2006 16Nov2006 23Nov2006 30Nov2006
03Nov2006 07Dec2006 13Nov2006 17Nov2006 24Nov2006 ip
04Dec2006 07Nov2006 13Nov2006.test 18Nov2006 25Nov2006 ip.org
04Nov2006 08Nov2006 14Nov2006 19Nov2006 26Nov2006

[root@ftp Delhi]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/hda2 ext3 4.9G 1.7G 3.0G 36% /
/dev/hda1 ext3 99M 8.3M 86M 9% /boot
none tmpfs 315M 0 315M 0% /dev/shm
/dev/hda6 ext3 27G 5.5G 20G 22% /home
/dev/hda3 ext3 4.9G 71M 4.5G 2% /var

how to troubleshoot this?
Plz guide me.......

Try explicitly telling fdisk which device to look at:
Do you get the same error?
Check the system log (/var/log/syslog, /var/log/messages), and dmesg output to see if there is any information there.

I've never seen this one before.

What distribution are you using?
Is this a new install?

Here's what I might try:
Boot your computer from a rescue disk (your install disk will do).
Mount the system drive using the rescue disk.
chroot to the system disk, then try executing the commands that give you the weird output.

If the commands still give strange output then I might suspect a hardware issue (perhaps a bad hard drive that's dying?).

If the problems go away then I would think you might have a bad install.

That's my suggestion. Hope it helps.

Could easily be that your disk is a damaged.
To check this , run a bad-blocks check
badblocks /dev/hda

Then it could be that only the filesystem is damaged (but I don't think you would get this Input/Output error, I may be wrong)
this will tell the system that /dev/hda2 (your / which includes your /bin) has been mounted 32 times without being checked. By default ext3 are checked after 30 mounts.

During the reboot /dev/hda2 will be checked.

Or my last idea would be that you are not using the correct harddisk driver. Is this installation new or is it a new problem?