This 4GB SDC4/4GBCR Micro SD does not function in an XP environment. It has been purchased recently and has never been functional. You can hear that the USB device is recognized by the USB insertion sound. It also appears on the Safely Remove Hardware list. It does not show up in Windows Explorer except once in a while it tries to appear as a storage device only to disappear. It causes a "not responding" message when you try Scan for New Hardware using the Windows Device manager although it appears to be in the list of USB devices. The supplier suggested a Microsoft Hotfix KBA but my XP uadates already installed it previously. Supplier also sugested that firmwary should be made available by the PC Manufactuer for hardware/software fixes. I looked for updated for my Dimension 8400 but there dot appear to be any. Any suggestions?