Spunky,

If I understand you correctly you have on two occasions installed N360 on top of NIS and it has gone OK.

If that's so the stick with it.

My reference to cleaning up was because sometimes it does not work smoothly and with a new PC or a Restored to Factory Condiditon I believe it reduces the risk of a faulty installation.

But if yours is apparently running smoothly then I'd not worry. The current Nortons are designed to install on top of each other and to begin by removing the previous one. They should even ask if you want to save settings etc for a reinstall or do do a clean install.