I think I found a solution to your teclast webcam as I had the same problem. First of all your teclast cam has a Vimicro chip inside, open the back by removing the 2 screws and read the number on the chip, (I needed a magnifying glass) then go to
http://www.vimicro.com/english/product/pc003.htm where you will find all the drivers for the vimicro chips installed in your teclast webcam. Find the webcam in your control panel, it will be a look312 then update the drivers (use have disk) and then point the system to the folder where you save and unzipped the drivers, it will find it and install it and it works. I has taken me almost 2 years to find the solution to this problem.
Good Luck