That shouldn't have happened by right. If you are CUTTING the file and pasting over, the file will only be deleted AFTER it has been copied fully. Are you running on FAT32? If you are, that must be the cause. FAT32 is intolerant of improper shut downs, like say you were accessing a file and you shut your pc off (for your case restart), the file will be corrupted. Windows will either delete the file or store it as some lost cluster the next time you reboot. How to prevent? Use NTFS. Provided you are on NT4, W2k, or WXP that is. If you are on any of these 3, look out for something like chkdsk.000 or similar on your root. It might be hidden so set your windows to show hidden files. Inside you will see weird chk files inside, change the extention to mpg or whatever your missing files were to see if you can play them back, and if you are lucky, you just might. All the best.