Now i'm not too familiar with these things, but to my understanding it is just a device that I hook into my macbook pro and it'll store all my MBP data into it, keeping it safe.
Correct. You just hook up the data cable (Firewire 800, Firewire 400 or USB 2.0 - Firewire being preferred because it is significantly faster) from the drive to your Mac, and the power adapter from your wall socket to your drive. There are also portable external drives that do not require a power adapter, but instead pull their power via the data cable from your Mac.
There are those that suggest that reformatting your new drive before you use it is a good idea, and I'm one of them. It is easy to do. There are good instructions here:
Formatting your hard drive for use with Carbon Copy Cloner / General Overview of the Features of CCC / FAQs - Bombich Software Support
Your external hard drive will show up as another hard drive icon on your desktop. You can backup your files to it just by dragging your Documents folder to its icon. If you want to backup everything on your computer's hard drive, though, it would be best to use backup software. This program is free and very popular:
Carbon Copy Cloner
Carbon Copy Cloner - Home
This one is $28, but some feel that it is easier to use:
SuperDuper
SuperDuper!
Apple also offers its own backup software, which does a different type of backup:
Time Machine
Apple - Mac OS X - What is Mac OS X - Time Machine
Now I need advice one which one to buy? Really I just need a 80gb one, or even a 60gb if it exists. I just need to save my school work, my music and movies.
As huge hard drives get cheaper and cheaper, the smallest available hard drives tend to become bigger and bigger. At this point its hard to find external hard drives smaller than about 250GB, and if you find them they tend to be old leftovers.
We just had a thread recently on which drive to purchase:
http://www.mac-forums.com/forums/switcher-hangout/228516-external-drive.html
Personally I recommend external hard drives from Other World Computing (OWC):
OWC Mercury Elite-AL Pro FireWire 800/400, eSATA + USB2 external Solutions up to 2.0TB - Plug & Play Quad Interface
...and I very much recommend *against* external drives from Seagate, Western Digital, LaCie and Iomega at this time. All of these companies have offered some very problematic drives of late.
Also, once I buy one, how would I go about rebooting my computer? Do I do it like I usually would or is there a specific way to go about this if I have an external hard drive?
As long as it is turned on before you boot up your computer, your external hard drive will automatically show up on the desktop just as your Mac's internal drive does.
You also have the option of installing the Mac OS on your new external drive (using your Mac OS installer disk), and then you can restart your Mac and boot from the external drive. The advantage of doing this is that you can use your external hard drive as your startup drive in case something happens to your internal hard drive and also for diagnostic and repair purposes.
Once the Mac OS is on the external drive, you can boot from it by either setting it as the startup drive in System Preferences --> Startup Disk, or by holding down the Option key while starting up or restarting.
I often use an external hard drive as a boot drive to test out and learn to use new versions of the Mac OS when they first come out. (As long as your external drive is connected via Firewire, performance is fine.) Using an external boot drive to run Disk Utility/Repair Disk, or, if you own it, Disk Warrior, is a quick and easy way to do maintenance.
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Randy B. Singer
Co-author of The Macintosh Bible (4th, 5th, and 6th editions)
Macintosh OS X Routine Maintenance
OS X Maintenance And Troubleshooting
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