Anyway, if I had to do a fresh install of XP these days, I'd likely stop at SP2 and be done with it. Disable IE, ActiveX, and the likes. No internet, no fools with their usb drives to wreak havoc on my games-only machine. No flash, no Java, etc etc. And before anyone says anything about "paranoidism" again, guess what, I don't f***in care about how you treat your machines. Staying clean is always easier for me. 😀
I've checked the games that I'd rather run on XP (EAX Advanced HD titles) and they never required anything above XP SP2. Even the games that mention SP3 (post 2008, so less relevant for my purposes) can usually run on SP2 as well. Of course, if you share the pc or use it online, latest version AVs and firewalls will usually require SP3.
If anything, I'd suggest you install whatever SP you want right away from fresh, and if you want to install, say, SP3 later, after you 'populate' your xp installation, make sure you have backup, if there's anything important. Sometimes installing hundreds of updates at once can mess with already populated systems (happen on ~5-10% of systems, said an IT manager, not me).