How do I back up my iTunes library onto an external hard drive?

[cq]

I can find the instructions for backing up onto discs but I don't want to do that as I haven't enough discs here and have a perfectly good external hard drive with loads of space on it and I'm sure there must be a way.

And I really need to free up some space on my hard drive, it's grinding to a halt.

I've tried exporting and I've tried 'save as' but neither seems to save it in a format which I can recover the stuff from.

Help!!!

Am sending this again at a more civilised hour in the hope that there are some helpful geeks now awake....

I don't use Itunes, but maybe this will help.
backup itunes