I saw a while ago Logos made the decision to stop support for Windows XP, but it didn't hit me until I saw in one of the comments that Logos 5 would not work with Windows XP! I checked the system requirements for verification.
I have a MacBook Pro running Apple's latest Lion or Mountain Lion, whatever that cat is, a laptop running Vista, an iPhone and an iPad, but my main working machine still runs Windows XP (I don't like MicroSoft's habit of changing things for the sake of change, nor their habit of excluding old hardware with new software releases).
I guess Logos 4 is where I stop, at least for the foreseeable future.