I installed it on my Hawwaii rig with no problems. However, after I shut down the Security Center and other useless added services (I had already shut down the security holes that SP2 closed), I couldn't see any good reason to install it on my Guam rig. Of course, I am the only one using both machines, use hardware/software firewalls, AV scanners, spyware catchers etc, and regularly update everything.