When it comes to USB devices, power requirements for them vary a bit. Although designed to produce 5 volts, many USB headers on the motherboard often produce only 4.75 volts -- especially the USB ports on the front of many PCs. This can be the result of many reasons, but poor case wiring is usually the culprit. USB flash drives or mice usually function OK with little less power, but larger devices such as full-sized external hard drives and optical drives may not function at all. If you have underpowered front panel USB ports, adding a powered hub can help.
Disconnect all USB peripheral devices. This includes all your flash drives, external drives, webcams, etc. Do not disconnect a USB keyboard or mouse without first turning off the PC. If you connected a USB keyboard or mouse to the front panel ports, shut down the computer and transfer the keyboard and mouse to USB ports on the rear of the computer.
Connect the AC adaptor to the powered hub. Plug the electrical plug for the adaptor into an available electrical socket. Plug the small end of the USB cable into the hub. Plug the larger, flat end of the cable into one of the front panel USB ports on your computer. Wait a few seconds for Windows to detect the hub and configure it for use on your PC.
Connect the USB peripheral devices to the empty ports on the hub one at a time. Wait for Windows to detect and configure each device before connecting another one. The voltage output from the hub should remain steady at 5 volts and adequately power your USB devices.
To ensure larger USB devices receive adequate power from the hub, connect larger external hard drives or optical drives to the ports closest to the AC adaptor connection. Although not a common issue, some hubs might deliver slightly less power to the ports farthest from the AC adaptor plug.