stepper motors not moving

Hello,
today is my first time to test the printer. But now I've a problem to use the manual control of the printer.
The Printer is connected to an win XP laptop. Serial USB Driver is installed.
Repetier give back the green connect symbol.
If I send the manual control command than I can hear a sound from the stepper motor. But nothing will move.
If I press the emergancy stop button than the sound stops.
I double checked wires, driver, different USB Ports.

I've no idea how to solve this issue.
Could you help me?

Holger