USB Extension

I am trying to help a friend with a problem. He has an external HD that has a very short USB cable. When he tries to add an extension the HD does not show up anywhere. We have tried 2 different cables and all USB ports. The HD is fine when connected directly.
Has anyone got an answer for this problem?
Thanks :confused

 

Do other devices work with the extensions? Are the 2 extensions you've tried the same make/brand? How long are the extensions? USB will not work on cables over 5 meters (approx 15ft) in length, and may not work on cables over 10ft (approx 3.3 meters) in length. If you have a powered USB hub, you could try to use it and it would probably remedy the problem. Even if the extension is fairly short, it could be the external is using up more 'juice' than can be transmitted through the extension, or the connection between the HD cable and the extension is somehow misfiring. Can you replace the HD cable with the extension?

 

Thanks for your response....
He tried his mouse and keyboard and they both work with the cable. The cables are two different brands. Both of them about 4 ft. He figured the first one was faulty and bought the second one. The 8" cable that came with the HD has a smaller connection that attaches to the HD, hence not interchangeable. We may have to get a hub. Any other suggestions?