The Pro edition runs a real-time scanner which, in theory, will intercept any malware and quarantine it before any damage is done. Unfortunately, in my case (Windows 7 64 bit) I've had problems with the pro edition. But, if it works for you, I would buy it as it seems to have good detection rates.
I install the free version on all pcs I get to sort out and always tell people that the pro version is better and that I have that. It works fine on xp 64-bit so I am surprised at problems with w7 64-bit.