P;reventing Spotlight from searching external HD?

Hi, (sorry about the typo in the title)

I have an external hard drive attached to my Mac, and everytime I search spotligh it comes out of sleep mode to be searched, this is really annoying as it takes ages to do this and I know exactly what is on the hard drive, as it is used for back up purposes.

Is there an option which will prevent spotlight from searching the external drive?


Thanks for any help.

 

Thanks for the quick reply, worked a charm.