There are several useful display settings available when using a dual monitor setup. One that can be used to control video playback content location is available on most video cards that support dual monitors.
Full Screen Video options can be disabled to avoid the behavior described.  Video card manufacturers refer to these controls differently so the two main manufacturer’s settings are described below:

NVIDIA Solution
NVIDIA refers to this control as Full-Screen Video Option and it can dictate how video playback is displayed when using two monitors.  The location of this control depends on which driver version you are using.

If you are using a Release 80 or older (version 89.xx and lower) you can access the control in the Advanced features tab with the following steps:

1. Right-click on the desktop
2. Click on properties
3. Click on the Settings tab on the Display Properties window
4. Click on the Advanced button near the bottom of the window
5. Click on the NVIDIA properties tab (typically has the name of the card on the tab)
6. Click on the Full Screen Video control in the left pane
7. In the right pane under Full screen device select Disabled

This will prevent the Full Screen video display on the second display.

If you are using a Release 90 (version 90.xx and higher) you can access the control in the new NVIDIA Control Panel:

1. Right-click on the desktop
2. Select NVIDIA Control Panel
3. Select the Video and Television category
4. Once open, under the “When watching video content…” section, click the radio button labeled “Only show it in my viewing application”
5. Click Apply at the bottom 

This will prevent the Full Screen video display on the second display.

ATI Solution
ATI refers to this control as the Theater Mode Option and it can dictate how video playback is displayed when using two monitors.  The location of this control depends on which driver version you are using.

If you are using an older driver with the ATI Classic Control Panel you can access the control in the Overlay features tab that ATI enables with their driver however this is only enabled in Clone mode and is not available in the extended desktop mode with the older driver versions.

If you are using a newer driver with the new ATI CATALYST® Control Center you can access the control there (full install required):

1. Right-click on the desktop
2. Click on ATI CATALYST® Control Center
3. Verify Basic is selected and click Next
4. Click on the Quick Settings tab
5.  Click on Video Playback under “Change a setting for…”
6. Click on Setup video Playback on the Second Display under “Select a setting…”
7. Click on GO
8. Once open, under the “In Extended Desktop show video” section select Standard Mode
9. Click on Finish

  This will prevent the Full Screen video display on the second display.

(DI006)