>I am using Tree control in my VFP application.
>This tree control is part of Comctl32.ocx and resides in Windows\System directory.
>Windows (probably window explorer) also uses it.
>If on user system, there is an older version of Comctl32.ocx then my application install set tries to over write it. Because ComCtl32.ocx is already in use, so an error comes on Window95 systems. This error did not come on Window98.
>
>Is there any way in Win95, to copy and register updeted versions of .OCXs that are currently in use.

You need to use a delayed update strategy; the Win32 Setup API has functions to do this. Rather than trying to use the API yourself, I;d recommend using an installation product like InstallShield (or even Setup Wizard) to create an update package.

Realize that in order for the update of a shared component to take place, the system will have to be rebooted, or at a minimum, Windows will have to be shut down and reloaded, so it's not something that can be done on the fly within an application without shutting down your application.