Earlier this week, pitse1eh posted some valuable dissertation advice so that you could learn from her and hopefully not make what she perceives to be her mistake (although something that combines that many things is bound to be interesting!). Let me add another: back up your files often.
As you might guess, there is a very good reason that I am sharing this advice. In the course of my dissertation, I almost lost one computer and totally lost another. Fortunately (for me), the computer that I almost lost was the one with my dissertation on it. "Almost" losing it means that I didn't actually lose anything on it, but it caused quite a scare. The second computer was E.'s and died while I was on a trip to San Diego; that one is completely gone—mechanical failure of the hard drive. Beyond my guilt at having everything on there gone (including some really sentimental photographs and our entire address book), the reason I was using it was because on my previous trip to San Diego (this is true, I only wish I was making this up) was when my computer had almost died.
Luckily for my dissertation, I had all of my work backed up (after the initial frightful scare of my computer almost failing the first time). At most, I lost a couple hours and probably a few months off of my life due to my dramatically increased stress level. But, the fact that I had two computers fail in a span of three months after having zero fail for four years seemed really odd to me. That was, until I realized that both of these computers (which were bought in our respective first couple years of grad school) were old and were getting more use than they had received in years. Suddenly, I was asking old machines to do a lot more work for me, and they were giving in.
Although this was a truly frightful and aggravating experience (particularly not backing up our personal files on E.'s laptop, which was just stupidity on my part), I learned in talking to people that it is not all that uncommon to have computer problems at the last stages of your dissertation. This could be a perfect manifestation of Murphy's Law or partially explained because it is easy to become careless as you are harried and stressed at the end of the dissertation. But, I think that it is also largely for the reason I mentioned above: the machines that we typically purchase in our first couple years of grad school just wear out by the time we finish. I would suggest delaying the purchase of your own machine as long as you can stand it (particularly laptops since they are especially prone to wear and tear) and, no matter what, always back up your files.
Why am I mentioning this now? Well, this week, my computer finally got too tired and passed onto the place where all good computers go—to join E.'s computer in the big computing center in the sky. Now I am sans computer at home, which means that posting is likely to be light from yours truly for a while. But, until I can offer more pearls of wisdom, please learn from me as well, and back up all of your files!