Depends on which version you have. Versions prior to '04 can be used on more
than one system without incurring additional cost through licenses. Of
course, once the one year subscription ends you will need to upgrade to the
next version. If you want continue to use the version you have, you will
have to reinstall the OS and start from scratch again if that's your choice.
In using any Norton's product, I've found it best to use the version that's
at least a year behind until all of the bugs in the latest version have been
worked out.
HTH,