Most software programs, include CAD, provide automatic backups. As you work on drawings, the software silently and automatically saves your drawings every 10 minutes or so. This is fabulous, because you will lose only 10 minutes of work (at most) when Windows crashes. (I set other, less intensive software, such as word processing, to automatically backup every 1 minute.)
The drawback, however, is that the backup files are stored on the same hard drive as the program (and probably your original drawing files). That's the default setting, because the programmers can only assume your computer has a single hard drive. Should that hard drive break, you lose your orignal drawings and the backup copies.
The solution is to tell the software to store backup copies on another drive. For me, that's an external hard drive hooked up to my desktop computer through a high-speed FireWire (or USB 2) connection. I like to have external hard drives for two reasons:
* If my computer screws up (ie, Windows really mucks itself up, or the internal hard drive fails), I can simply move the external hard drive to another computer (even a notebook computer), and keep working.
* If a disaster befalls the office, I can easily grab the external hard drive(s) and remove them from the area.
Alternative approach: some firms store the original drawing files on a central server computer, and keep the backups on the local desktop computer. In any case, go into the software's backup options (probably found under Tools | Options) and change the location of the drive on which backups are stored.
Should you worry about hard drives breaking? Yup. Amongst the seven computers (and 11 hard drives) in our office, we typically have one hard drive go each year. Some people have expressed the conjecture that external drives break down faster than internal hard drives due to heat, because the external ones are not ventilated well enough.