VGA Cable unable to connect to compaq presairo desktop.

Hello,this is my first post here i need help,
i have a compaq presairo desktop running on windows 7 professional.I ma using a VGA cable to connect and use my desktop to a Sony Bravia KLV40S400A LCD TV but one day morning it stopped working,i tried everything i reconnected cable,done everything i even tried connecting my desktop using that vga cable to a HP compaq monitor that i buyed earlier but still it just display a black screen