Installing JDK 7 is not possible on a machine without admin rights or without knowing the admin credentials on windows. Earlier there used to be a zip version of JDK shipped by Oracle/Sun but now the company only allows downloading and installing the exe version of the JDK.
But it is possible to use JDK 7 without installing the same. All one needs to do is download the JDK from the following URL and then set the corresponding JAVA_HOME, PATH and CLASSPATH variables.
The above provided JDK is same as the one which gets installed on the windows machine but the installation folder has been zipped and uploaded for the convenience of developers.
So now download and use JDK without worrying about admin rights.