Flash drives by nature are not reliable media. Never store data on flash drives you cannot risk to lose. Always make a back up. Some brands are better than others, but static RAM storage by nature is not 100% reliable. Some brands are notorious for unrelaibility - Sandisk cruiser is one of those brands to avoid. If your flash drive "wigs out", you may be able to restore functionality, however data recovery in most cases will be catastrophic. A frequent loss of data on flash drives is the corruption of the boot sector in the static RAM. Because Windows operating systems treat flash drives like "mini" hard drives, essentially what you have is a corrupted hard disk which must be reformatted to recover functionality. Before attempting a format, see if the drive can be read in another computer. If it can, great! Attempt to move the data off to salvage. If not, flash drive errors can also be caused by bad or corrupted drivers on the host computer. Not all flash drives export drivers to Windows or the drivers are local. Try to download the driver (if any) for your flash drive from the manufacturer. Then attempt to re-seek your drive. If neither of these attempts work, assume the data on your drive is toast. You will be forced to low-level format the drive in order to restore functionality. Before attempting to do so, try a few data recovery programs like undelete or pc inspector smart recovery. I have had luck in the past with both programs, particularly the latter. If that is still a no-go, then a format recovery attempt is your only alternative. You are guaranteed to lose data, but you may salvage your flash drive. 1. Find a computer with Windows98 (I think First Edition will work, but I used SE) and then download and install the driver for it (Windows98 requires a driver to read the drive). If you don't have W98, then go into XP. Control panel -> Computer Management -> Disk Management 2. Plug in the your Flash drive / Memory Stick 2b. The drive should appear, try and open it and get all your data off, if the drive doesn't appear there may still be hope (details later). 3. Format the drive as FAT32 under W98. Under XP right click under the flash drive letter. Ensure it is your flash drive, not your hard disk! You will lose all data when formatting. 4. Recopy your data back, and plug it into an XP machine (if using W98), it's fixed. Now if 98 didn't see the drive, there is an HP utility for formatting USB flash drives, do a search on these forums for HP and Sandisk and format and it will probably come up. Try that, if that doesn't work, I'd say there is a 90% chance your drive is hosed.