The reason is likely because the pin assignments in the video cards of several manufacturers, actually. We had a lot of these complaints with the "A" series, and what's happening is that there's a ground pin that isn't telling the television that "hey, I'm a VGA signal, and I'm here! Accept my signal!". (In 2009 and moving forward, we turned the PC input into an "always on" connection so that the experience would be much more enjoyable).
There are three things you can do:
1. First, know - or learn - how to send video through your computer. Some people have laptops, and to output the video requires either a setting in the display drivers menu, or a FN+(F-key) combination. (Toshiba's are generally FN+F4, Sonys or Dells are FN+F7 or FN+F8, etc...)
2. Second and easiest - update the video card driver and retry step one.
If you plug the VGA in, and you can see your boot screen - and then it goes blank, then it's a Windows driver or the resolution is not set correctly.
If you see "Mode Not Supported", then the resolution isn't supported.
3. Try a different VGA cord. A cheap one may work just as well as an expensive one. It's worth trying.
OPTIONAL: Update the computer's BIOS. On several manufacturers - many of which I cannot name - the pin assignment was fixed, and a BIOS update was released for some computers that does fix this. This was a manufacturer's suggestion to a customer who posted that on the forums - this is NOT a recommendation from me officially. If you do NOT know what you are doing, seek keep from a professional, or do not do it.
Keep me posted. In almost all of the posts I've seen, one of these methods has garnered success.