Scanner help!

I had bought a scanner/coder for my car off of EBay a week or so ago and I sent it back because it would not read my car. Than I realized I needed a 20 pin connector do I bought that as well. The problem I am having is getting my computer to recognize the scanner is connected to my computer. I have tried two different computers both running windows 7 and have had no luck. I did install the drivers and do all the steps that made my first scanner work before I sent it back but now my computer won't recognize that it is connected. Also the last scanner I had would connect but when I tried to scan my car would come up with a connection error to IKE and EWS and would not read anything else. If you can help I really need it. Thanks