Bob, you have tried installing on XP SP2 and Vista 64 bit to no avail do you think that it might just work on Vista 32 bit.
Might do but then I doubt it fails to install on every XP Pro system either. My serious issue is that it should fail to run at all. DxO Optics also suggest that to get it to run you have to turn off DEP (Data Execution Prevention). I have done some C++ programming over the years and I never felt the need to write code which executed data. That admission alone is enough to confirm me in my view that I want nothing more to do with DxO Pro v5.