Hey,
There are many websites that let you download Youtube videos to AVI. I will like to suggest those websites which I have been using. Those websites are free to use and let you download without asking for you to subscribe.
1) Ytmp3conv
I have been using this app for a long time, I personally like this app because it is really easy to use and free.
2) Ytbconverter
You may try Ytbconverter this is another website that will allow you to download youtube videos to AVI.
3) youtube2video
This is last but not least, website that you will like to use to convert youtube videos to AVI.
I hope, it will help you.