I have kaspersky internet security 2007. I like it, but if the security pop-ups annoy you, you might just wanna try something else. It seems to to take a lot to teach the firewall and with vista x64 it adds to the work. If you want just an av software try: nod32
I Use vista on my laptop and Norton Antivirus 2007 is working great on it and it has less popups than kaspersky actually nothing. I am so impressed by it.It doesn't slow down the system by much either.Also I Use nod 32 in my desktop it is also great but virus detection rate is less than Norton and kaspersky.But it won't slowdown your system.