One way to use FirstDefense_ISR is to check out programs with a safe snapshot to fall back on if necessary. This is pretty straightforward if testing a new program or trial license. How about paid for licenses - could there be technical / renewal issues? For example if your AV just offered a new version and you know from reading threads here that some users find the new version buggy. Having F_ISR would let you test the new version in a snapshot to come to your own conclusion if any of the issues mentioned elsewhere actually affect you. If necessary you can go back to your proven / stable version by rebooting to your primary snapshot. What I am wondering about is if the software vendor may get confused if you obtain an upgrade via snapshot 2 and subsequent further definition updates this week and then next week reboot in primary and get definition updates for your old version too. A week later you may decide to test the new version some more ... Legally I think it's a non issue like installing / uninstalling / installing... the same program on the same pc several times. However, has anyone ever encountered technical issues, perhaps having the licence questioned since it may appear that your licence is installed more than once?