It is a very bad idea to have all your data on a usb flash drive or similar memory card. I have had them go down with no warning, unfortunately at the same time as my hard drive had a fit. I nearly lost all my data. Always keep any data that you cannot afford to lose in three different locations. For example, your hard drive, dvd and flash drive, or another computer.

Flash drives should only be used as a transfer medium where you have the original file elsewhere, do not use them as an archive.