Melissa's son is trying to upload videos with her iMac, but she's having issues now with drive space. She has a 1TB hard drive backup and the iMac says there's too many items in the "startup disc." Leo says that's the internal drive, and it's full. Leo says Junior is not taking the videos off after uploading them. There are programs that would let her look at the drive graphically to see what can be removed. Anything over a 1GB in size should be moved over to the external drive and removed.
That's not really a backup though, so Leo recommends getting a second external drive for that. He prefers the Western Digital My Passport 2TB drive at Amazon, or the Seagate 2TB drive. Or she could even get a 1TB drive for under $100. Drives are cheap these days.
Leo also recommends running SuperDuper, which will create a bootable backup from the external drive.