First, please make sure that you have installed Anti DDoS Guardian correctly. You need to log on Windows as a real administrator and run from there.
If Anti DDoS Guardian was correctly installed, then the problem may be caused by not allowing unsigned driver software. The following image shows the configuration of driver signing options in Windows XP. Please select "Ignore" or "Warn", do not choose "block". The "Driver Signing Options" dialog can be showed in Windows XP by following steps:
1. Right click "My Computer" icon and select "Properties" menu item.
2. "System Properties" window shows and select "Hardware" tab.
3. Click "Driver Signing" button.