I have Norton 360 installed on 4 computers and it works great on 3 of them, all with Windows 7/8. But my favorite old desktop, a Dell 8250, Win XP Prof, Service Pack 3, with1.5 GB RAM, has become so slow as to be unusable. I tried everything, defrag etc, uninstall, reinstall and all the other Norton suggestions to no avail. Windows task manager showed that slowing was from 100% ram usage, and from performance data from Norton 360, showed Norton was causing the problems. SO.... since it was either fix or abandon the computer - it that slow, I finally went and totally uninstalled all Norton products through the control panel. Guess what? Problem completely solved. And the computer is now working fine, Fast as it ever was. My old desktop with Win XP still gets the jobs done, just not with Norton. ( I am using with latest version of Firefox for Win XP which also works great).