When you initiate an uninstall via the Add/Remove Programs applet, the display is refreshed after the uninstall and the uninstalled product no longer listed.
If, however, the uninstalled product drives the uninstall of other products also listed in ARP, then those products remain listed until ARP itself is refreshed, such as by closing and re-opening ARP.
Is there any way to prompt the refresh of ARP from within a custom action, so that all the uninstalled products are removed? I'm guessing this would be a SendMessage of some sort, but otherwise don't know where to start.
Without having tried it, my first guess would be to try calling SHChangeNotify. After that, I'd look into SendMessageTimeout+HWND_BROADCAST+WM_SETTINGCHANGE or suchlike...
