My g-drive has started making a cli...

If that sounds click-click-click-click like the reader is going to the first read then park again and loop. It sad but I think its already giving up. If you can still run it for a while better to backup what's important that it can still get.

Some software from manufacturer might help. But its signs for a replacement.

clicking sound on hard drive can be one of two things

1stly a virus can cause the drive to stick and click the arm. use a good antivirus programme. Avira Antivirus is the best free remover.

http://download.cnet.com/Avira-AntiVir-Personal-Free-Antivirus/3000-2239_4-10322935.html?part=dl-10322935&subj=dl&tag=button&cdlPid=11012914

2ndly The harddrive arm is sticking and there is a way to help it along but this is dodgy. The solution is to hit the drive pretty hard while powered off to the side, the action is to free the arm not damage beyond repair. Do this at your cost.

option 1 is better performed first.

AndystUK
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External hard drives are quite prone to this
The clicking you hear is referred to as the "click of death" as far as hard drives are concerned. And I am afraid it is as it says.
It was probably knocked, dropped, or maybe just mis-handled.
These are hard drives and not flash drives. As such should be treated with care
If it is truly dead and you MUST have the information from it then the only real alternative is to send it to a data recovery expert.
These services are NOT cheap
Sorry for the news