I believe this is a similar question that ws recently asked. I do not thinkthat question was resolved. it has to do with how WindowsOS performs its processing of running applications and/or services.
there are third party apps that override some OS registry entries to lock and prevent background processes from moving to the foreground. I hear, TurboTop and i believe TweakUI may work to prevent that. In addition some windows software contains options for "always on top" I believe firefox has an addon, process explorer, and vlc media player are examples. maybe google some of the users common software to see if this option is available
after browsing some windows forums. It seems to be a hot topic. Windows XP had a setting that would prevent applications form stealing focus from active windows. However, it seems like that feature was removed in win7 and beyond. The argument is that developers are responsible for not including the focus in their applications and not MS propblem to prevent it.
maybe this link can help windows - Preventing applications from stealing focus - Super User