All usb port disabled after Win7 start

Hi everyone,

I just brought a few ProDesk 600 MT. After setup operation system, one of them seems locked all usb port after win7 start.

I can use keyboard/mouse during start up, including bios or the windows safe mode selection menu. However, once win7 started, all usb port are disabled, not even power supply. Which means no keyboard, no mouse. I can't do anything except power down the computer by push and hold power button.

Does anybody know why and how to fix this issue?

Thanks

Alan