In order to use the V-Ray animation, go to the V-Ray Options menu and go to the 'Output' tab. At the bottom, you should see an Animation section. Just check the box next to 'On' and then set your desired frame rate. Vray doesn't actually make avi files. It simply renders each individual frame as seperate image files. You can choose the image type and location where you want to save all the frames by checking the box next to 'Render Image File As'. Once all of the frames have been rendered, you need an avi creator program to compress all of the frames into an avi file. (Quicktime Pro is the most popular for this. There are some free software online that do this too.)