When ASUS UX21E series uses USB 2.0 under Windows XP, please be sure to update to SP1, otherwise an error message will appear: "You must add a HI-SPEED USB host controller to this computer to obtain maximum performance". The solution is as follows:
1. Please press F2 to enter the BIOS when booting and then go to Advanced->Chipset->Southbridge ->Confirm that the USB1.1 OHCI Controller and USB2.0 EHCI Controller options are both "enabled" (only some models have this option).
2. Please go to Control Panel->System->Hardware>Device Manager->Universal Serial Bus Controller to confirm whether there is a question mark, cross or exclamation mark on the front of the device.
3. Please remove the driver of the USB device and install it again.
4. Please confirm that the USB device can work normally on other computers.
5. Please confirm that other devices can work normally on this computer.
6. Please update to the latest version of BIOS.
7. If possible, please connect the USB device to an external power supply.