A long time ago i tried to jailbreak my iPad1. It failed, but my iPad worked perfect, except Cydia.

Today I wanted to give it another try, so first I tried to just update to the newest iOS through iTunes. The update failed and on my screen a white usb cable pointing to the iTunes logo was visible. The worst thing is that iTunes doesn't recognize my iPad anymore. I tried to activate DFU-mode, but it failed.

Can somebody help me please?