My hard drive is one year old. I bought it in 2008. But the oldest file on it dates back to November 24th, 1997. How can I have a file that's 11 years older than the drive? Good question.
For you see, in the past 11 years, I've upgraded several times. Sometimes it was because I had money and a newer, faster, bigger, better hard drive was for sale. Other times it was because the drive was in imminent failure, and I had to upgrade or lose my files forever. My newest drive is 1 (manufacturer's) terrabyte, which is larger than anyone could have even dreamed of in the past.
But as for my file, I have kept it all these 11 years by copying it. Each time I got a new drive, I would format the new drive, copy over all my files, and then erase the old drive. Depending on how good the old drive was, I could move it to another computer, use it as a scratch drive, or just destroy it and throw it away.
So how did I get a file older than the hard drive? Well, when I copied the files over, they kept their times. After all, copying the file doesn't create it all over again, it makes a new file last modified at the time of copying, but created at the time as the original file. This makes sense, right? The copied file is not new information. So because of this, I can have a file back from 6 copies ago. Or 100. Or several million.
In related news, people are worried because of how information is stored on hard drives and CDs, which will all be completely dead within ten years. Unless this is archived, there is a good chance that it will be lost forever, and future historians will have a massive gap with this portion of history.
This need not be the case. Egyptian stonework, 4000 years old at this point, is as legible today as when it was carved. (Although it has deteriorated slightly. It used to be much prettier.) 4000 years is quite impressive in the face of 10.
I do have to wonder about what to chose to preserve. Everything ever posted on the Usenet networks has now been preserved by Google, using massive effort to save every last byte of it. And while some of it is significant history, much more of it is pointless trolling, flaming, and spamming. This is also being preserved at great expense. Perhaps Google does not want to appear biased in their preservation.
I mean, we do not have every, say, medieval manuscript ever made. Many were erased as a way of recycle paper, or tossed in the fire because some lord decided it was useless, or left in a warehouse until it rotted away. Would it impoverish future historians to not have some of the lamer groups (Hypothetically let's say: alt.flame.picard-is-better-no-kirk-is-dammit) to read and see how much excessive free time some 20th century humans had?