USB problems

Hi.
I have a new USB flash 8 GB, when i copy files on it (or use the “send to”), documents are there. once it is removed from the PC, if used on the same PC or on another PC, it is like empty (properties show that free space is 7.79 GB). I scanned it for viruses on different softwares/PCs, formatted it… it does not work. Please, could you help??
10x 🙂