I have a Mac Book Pro 10.5.8, and I'm planning to get an external hard drive to back up ALL my information, but first I'm guessing I need to see how much room is in this lap top so I can make sure I get an external Hard Drive that has just as much if not more...

Please help, and if I'm wrong please let me know...

Apple > About this MAC > Software Update > Serial ATA or ATA (left pane) > Look for Mac HD Capacity