Ya I keep my XP patched, and ya I'm talking about the non-pro version of DTX.
If I remember right, and it's been awhile, regarding the non-pro, I think "trying" the 4 version and the going back to the 3.5 was, uh, problematic. And I think trying to load the 4 without uninstalling the 3.5 first might have been problematic too, not so sure about that.
Anyway, in terms of just loading 3.5 non-pro on my XP box straight away without monkeying around with other versions, it's as fine as DTX ever has been. The permissions for a non-admin user do need to be opened up though, things want to modify and write to the Programs sub folders.