Java runtime won't start

Since I have installed winrar on my Windows 7 (x64), all JAR files just won't work anymore. I'm trying to start BDSup2Sub.jar

I googled it and found: With the Java runtime installed, the JAR can be started by double clicking on it. Alternatively, you can start it from the command line via: java -jar BDSup2Sub.jar or javaw -jar BDSup2Sub.jar in CMD.

But I don't know how to do this in Windows 7 or in CMD..