Internet explorer is highly risky, that's where most of the security holes are located. Firefox is a great replacement. And Service packs are definitely important they plug some of those security holes and it's RARE that they will mess up your system. If it does, then most likely you already have an existing issue and needed to reload anyway. My husband is a computer/network/security expert, so trust me on this. I don't use XP because it's so bloated, switch to 2000pro if you can. All the computers in our house now are on Linux, except mine because Windows is just getting worse and worse.