Dr JIm

I have a problem with my 2003 Audi A4 3.0 convertible. My battery was totally dead this morning so I put on my battery charger and attempted a boost to start the car. All i get is a clicking sound. I also noticed a sound under the hood (seems to be near the firewall on the passenger side of the engine compartment) that sounds like a small fan or electric motor running and the only way to shut it off is to disconnect the battery. I need some help troubleshooting this problem and thank all in advance for submitting their solutions.
Second, I disconnected the battery but am unable to lift it out - is there a concealed fastener somewhere?