I do not agree 90% of the flash drives sold on eBay are fake, because there is a £500 Paypal Protection. Personally I support No-Frill OEM products on eBay because they offer fair price and beat High Street Rip-Off.
If you pen drive or mp3 player is showing 'disk error' or 'not recognised' when plugged in, it means
1. The drive is not properly formated by the manufacturer, and this is called Low Level Format, which can not be done without special software. Format under Windows is High Level Format (search these terms in Google);
2.Hardware Problem, in this case you need to return the item to your supplier for inspection;
3.Fake item, the internal ROM has been hacked.
To repaire or 'EDIT' your Flash Drive's ROM, you may download a software called UMPTOOL, which most manufacturer use it to modify the firmware. This means they can hack the firmware information to something not real. However, as an end user you can use it
1. as a tool to Low Level Format your drive;
2. to see NAND memory information;
3. as a tool to detect if your item has been hacked!