Normally when plugging in USB 2.0 emulator and following the procedures in the manual, the driver could be successfully installed. Under certain circumstances, when user gets a yellow "? " or "!" message in Device Manager, it means the driver are not properly installed. To solve the problem, unplug the emulator, open "Search" in the Windows Start menu. Search for "oem*.inf" file which contains "Ez-embedded" content, and then delete the file you found (for example: "oem8.inf" ). After that, delete both "C:\WINNT\system32\drivers\Ez-embedded1.sys" and "Ez-embedded2.sys" file. Re-plugging emulator, go to Device Manager, use "update" function to re-instal the driver. If the problem is still unsolved after trying above steps, please check the connection between the device and your PC.