Of the 90% of computer users who store personal information on their computers, about 24% report that they have lost personal information in the past month, generally because of system crashes, according to Harris Interactive. Of those who store personal data on their machines, only 57% back up their data. Among users who don’t back up their data, 34% said it hadn’t occurred to them to do so, while another 31% said it simply wasn’t important to them.