Many people who don't have their heads stuck inside their PCs all day get confused about how much memory they have (which we technical people label RAM) and how much storage they have, which we techies generally label "disk space".
Many's the time I have helped a friend or family member who is "running out of memory" and found that the issue is more about their storage than their RAM. Nowadays, with a cheap computer running 1GB, 2GB or even more memory, this is less common, but it seems no matter how much disk space we put in our computers, we're always running out. Family photos, videos, games that come on multiple DVDs, movie libraries - soon even the largest 2TB disks seem restrictive.