It's simple. You just need to the use the noConflict method. noConflict relinquishes jQuery's control of the $ variable.
I've written a small code snippet below.Here the page first loads jQuery v1.3 and then v1.7.1.
As soon as the later loads I call the noConflict method and define an alias in order to use version 1.7.1. Now if you notice "$" gives me access to v1.3 while "$j" is v1.7.1 specific.
Till next time ...