What does bad sectors on external hard drive mean

First use a hammer to distroy the Platters.

You could try downloading the manuf utility disk and check the drive, But if it is (A) old) and (B) small size, then probably not worth it.

The Hdd is only approx. 1 year old and is a 250gb Zendi hdd , I did check there web site but there is no downloads available so i have emailed them with the issue . Fingers crossed they will send me the software .  

Sounds like it might be

Try running a chkdsk on it (assuming you're running Windows).
chkdsk ?: /r (where ? is the drive letter).

If XP: Run: CMD, then type the above
If Vista/7, type CMD in the Start/search box, when it shows up at the top, right click and select "run as administrator". Then type the above command.

If that returns bad sectors, then it's not a healthy drive. (chkdsk with that flag will try to fix things, if it can. In it's final report, it will tell you either way what happened).

Tried as you suggested and i apreciate your help , but when i got the box to open to type the command , there is no option at the top right to "run as administrator"
i did type the chkdsk , but it did say i didnt have the rights .I am using windows7 OS
Thanks

Have to right click before you select/execute CMD
Start -> type CMD -> when "CMD.exe" shows up, right click (not left click) and select "run as administrator". If the CMD box (the black box you type in) is open before you right click, you went 1 step too far   )

You could have the admin protection disabled, but based on the error message you shouldn't.
If you're on a work-controlled computer, it's possible your administrator has disabled your access.

EDIT: RetiredChief's suggestion is always a fun one... hammer + computer parts = loads of fun  

I did as you had said above and opened as administrator and typed in the command again , but still came back to say " Acess Denied as you do not have sufficient privileges. you have to invoke this utility running in elevated mode "
I really appreciate your help. Thank you

Hmmm that error message is typically what you get when you don't use "run as administrator". Strange.
If this is a work computer, then I can understand it, if not, still scratching my head.

An alternate route is to do it through the GUI (My Computer, right-click on the external drive, Properties, Tools tab, Error checking - make sure both boxes are checked.). See if you can run it that way.

Last resort, break out that hammer.  

On Last Possible method would be to remove the HDD from the enclosure, connect it direct to the computer.
Two options:
1) again try the chkdisk command and/or from My computer, or
2) down load UBD (it has several disk utilities) to check the HDD. It is an Iso and will provide a bootable disk. Note, it has many more utilities on the disk such as memtest86.
List of Utilities and download button on left side: http://www.ubcd4win.com/contents.htm http://www.ubcd4win.com/contents.htm

Yes great got it running   Thank you once again , does this checker take a long time to go through , it seems to be taking its time   ?

yea, can take a couple/few hours