Sorry I did forget to mention that I am unattendant updating a lot of PCs (Win XP SP3) using install_flash_player_10_active_x.msi. This file updates the files in C:\WINDOWS\system32\Macromed\Flash\ (Flash10l.ocx, FlashUtil10l_ActiveX.dll, FlashUtil10l_ActiveX.exe etc). On some of the PCs there is also a file called NPSWF32.dll. As I understand this is used by Firefox?
But how can I update the NPSWF32.dll to the latest version running an unnattendant installation? I have found info about a file called NPSWF32_FlashUtil.exe but have not yet found from where I can download it.