>But surely we can expect plenty of service packs for Windows /*vbg*/, and each would have the latest VFP runtime, no?

What if you had a custom property on a form called foo, then a new version of VFP was released with a new foo property. When the VFP runtime files were updated on a machine from an operation system patch/udpate, your application would break. I think developers need to control when the VFP runtime files are updated on a machine, not an operating system update. There are other factors to consider also, besides that fact that the VFP runtime files are not considered system files and therefore would not be included with any core operating system installation.