After Connecting External Speaker Laptop Speaker not Working ?

I am facing a problem guys so I have a Windows 7 Laptop and I have connected an external Monitor to it the MOnitor does not have a speaker so I have ourchased an external speaker which I have connected to the 3.5 Headphone Jack in the Laptop. The Audi plays perfectly fone when I connect the speaker, BUt when I remove the speaker from the Laptop, and when I try to play audio directly from the Laptop there is no sound coming from the Laptop speakers, and they were working fine till about 2 MOnths back. I am sure there has got to be something with the settings and not the speakers of the Laptop have gone bad.

Check this Video if it helps.