Hi Toast, in general, I am trying to avoid distribution of old versions, because LaunchBox has been developed so quickly and there have been plenty of versions out that have had so many issues. Really, though, the latest versions of LaunchBox should actually be faster and use less RAM if configured properly. Have you tried using the latest and turning off the RAM cache under Tools > Options > RAM Cache? Also, using default Windows styles might help some too.
Per the "not officially supported" thing, I believe the only stuff that doesn't work on XP are the wizards, as they use Vista+ controls. So I would still very much recommend using the latest release, and just turning off the RAM cache. If you still have performance issues and feel like it was faster and used less RAM with the 2.x releases, then something isn't right. The 2.x releases were pretty wasteful with resources, especially RAM.