Thank you Sandie

There is. Once you've added the picture you can return to the edit page and there will now be a Car Location box (second from the bottom). If you click on the Select on Picture link you just need to click on where the car is located on the picture and a box appears around the car.

Is it possible to highlight a certain part of the picture to identify the car of interest? I have seen this several times but cannot seem to find the option to do this. Thanks

Thank you, Raul!

YTD Downloader is also good for downloading from Youtube.

http://download.cnet.com/YTD-Video-Downloader/3000-2071_4-10647340.html

Thanks!

PrintScreen key is not the best way to make captures anyway
For Youtube, the best solution is to get the file using JDownloader or http://www.bestvideodownloader.com/ for example (I use their Firefox Add-On)
This allows to get the highest quality available.
Once you have the file you can make captures with the programs mentioned previously (MPC-HC or VLC for example).

The problem is that when I press PrtSC I obtain nothing (I tried on YouTube).

Indeed, it provides the image in the original size. On DVDs the picture use non-square pixels so they are not stored in the same format as they are displayed, hence why they have to be resized. But since you always have to also remove black borders, both can be done at the same time in xnview.

Thak you very much, guys, I will try, but not today and not tomorrow, I don't have the courage to try again, yet.