Defintely on. You may need to set your system to a restore point if you get a very bad virus. You may say that you think your protected, because I have anti-virus and a firewall. That is would I said and turned off system restore to save disk space. And what do you know, 1 month later ended up with a bad virus. Pop Ups, Keylogger, etc... I had to reformat my hard drive and back up all those files. Trust me, turn on system restore.