Samsung LED Monitor with TV Tuner Card (External)

Hi,
I have a Samsung SyncMaster S22B370 (22 inch LED). It is connected with my PC with HDMI Cable. I recently bought Intex external TV tuner card.

I have a spare VGA port on the monitor and when I am trying to setup it with VGA cable. If I use it when PC is turned off, it works. But when PC is turned on and if I turn tv tuner on, it is not detected. This tv tuner card has inbuilt function of PIP (picture in picture) so technically it should show small window of live tv while working on PC.

Thanks in Advance.

-Umang