This is an unofficial release.
It looks like someone at Virginia Tech has taken the standard available Spice 9.1 student release install:
http://www.eng.auburn.edu/~troppel/91pspstu.exeThey have packaged it up with all the DLL's it requires and turned it into an installation-free executable.
There are programs like Portable Apps
http://portableapps.com/ that allow you to do something similar.
There are other alternatives - just cannot think of them off hand.
Richard.