@ gate1975mlm
I would say that the web shield is perhaps the strongest pro-active shield as it is A) very accurate in its alerts and B) it is stopping them from getting on to your system, rather than rely on detection on the system. The web shield can detect and block exploits/hacked sites, that are going to try and run scripts to download other malware.
Now the beauty about this is that avast doesn't have to be able to detect the remote malware, just the exploit/script injection on the original site. So this could prevent what might otherwise have been undetected malware getting on to your system. So no contest install the web shield.
Given your system spec, I honestly can't see the web shield making a blind bit of difference to its performance. I have no problem with performance on my system with the web shield enabled (I don't have P2P or IM shields installed, don't use those products) and our system spec is close, my processor is faster, but not by much and you have more RAM. However, win7 will be taking a larger chunk of that RAM than XP Pro.
