Tcl-only actually available to Perl with http://search.cpan.org/~vkon/, that CPAN module makes available perlTk or pure-Tcl syntax, at your wish.

See my post about video on perlTk at Re: Video components for Tk?

Also you could follow links at the bottom of my home node id to get an idea how to do the trick.

Win32-specific answer to you question is using Win32::OLE to manage existing registered media player.