What's the best way to back up an external hard drive onto a Macbook? A friend of mine has a Macbook Pro, and an older 80GB external hard drive.

She is copying files from the external hard drive (which contains all her work) to the Macbook, but slowly because she's reorganizing the data at the same time. 

I would like her to back up the external hard drive onto the Macbook, which has 750 Gigabytes of space, just in case something happens to the external drive. 

Is there a quick, easy, preferably built-in way to do this? I would prefer a method that doesn't copy files separately (so as not to create a second location on the machine that contains all her work, gets indexed, etc.) but takes a disk image and stores it somewhere. The goal is just to have a quick snapshot in case anything goes wrong.
You can use Disk Utility to create an image of the external hard drive.

Plug in the external hard drive and then start Disk Utility--it's in the Utilities folder under Applications--and then select the external hard drive from the list along the lefthand side of the Disk Utility window.  Once you've selected the external drive, click on New Image at the top of the window and it will ask you where you want to store the image file.  Select a location and then let it do its thing.

Once completed, you can restore the image to the same or another external drive or you can simply double-click the image file to mount the disk and explore its contents using finder as you would normally.