Need a part identified.

I have an 03 Crown Vic Police Interceptor fully loaded. Just bought on 07/07/12. The car ran fin untill the battery died. I found out that the negative battery treminal was loose and that's want caused the battery to drain. Now the problem starts. There is small square metal box in series with the positive side of the battery. IE The positive cable connects to one side if the box and the other side of the box connects to the positive terminal of the battery. I tried to jump start the car from the positive and negative side of the battery as normal but I got nothing. No ignition bell, Radio, Interier lights, idiot lights etc. I connected the positive side to the lug BEFORE the box and the car started but ran for a short time then stalled. This happened repeatedly. I then ran a "Jumper' between the lug before the box and the positive battery terminal and it starts OK. I am afraid to leave the jumper on because I'm sure that the box is there for something. I just don't know what. I am going to try to upload a picture of it. I sure hope someone can help. I do not want to burn out the wiring in the car. I will not run it untill I find out what to do. Thanx in advance and I am truely sorry if this is long winded.

Don't worry about sounding long winded. The more information you ask, the easier it is for someone to answer.

If the "metal box" isn't sealed and can be opened, look inside. It may be a fusible link or part of an alarm system someone added because they were having trouble with the car. I would have no idea as to what it could be.

If the car starts and runs okay once you have bypassed the box, I would replace the positive cable with a good cable and get rid of this box completely.

If you don't have a Chilton manual handy, go to this link to see what it shows in the wiring diagram.

http://www.cb7tuner.com/vbb/showthread.php?t=147239

Thanx for the reply.
I bought the car from a dealer that got the car from a police department that he has a contract with to buy their old police cars. That's why I kinda doubt that it is part of an alarm. I tried disconnecting the positive cable before the box and connect it directly to the battery (after the box) but when I do, I get nothing electrical. Almost like the battery is disconnected. There are other wires connected to the box. That's why I'm afraid to bypass it. Is there a way that I can upload a picture with my message? If so, Maybe someone can identify the part. Thank You, Also, for the link to the repair site but since mine is a police car with a lot of non factory parts, I'm afraid that it will not help
Below are links to a pictures of the mysterious box.

http://www.supermotors.net/getfile/933142/fullsize/000_0394.jpg
http://www.supermotors.net/getfile/933143/fullsize/000_0395.jpg
http://www.supermotors.net/getfile/933144/fullsize/000_0396.jpg
http://www.supermotors.net/getfile/933145/fullsize/000_0397.jpg

Have you tried to see if the "yellow" button on top can be pressed up or down, OR from side to side? There may be a switch inside to reset it.

How does the hood close?