In the Windows Media Playlist Editor, expand the playlist, and then expand the smil element to show the elements in the playlist.
Click the element after which you want to add an advertisement.
On the toolbar, click the Add element arrow, and then click Advertisement.
The Add Advertisement dialog box appears.
Type the location of the advertisement you want to add.
Click OK to add the selected advertisement to the playlist.
Notes
The Windows Media Playlist Editor is only available in the Windows Media Services snap-in.
Content streamed by Windows Media Services must meet the minimum supported content length of the player to ensure reliable playback. The minimum supported content length for Windows Media Player 9 Series is 5 seconds. The minimum supported content length for previous versions of Windows Media Player is 30 seconds.