When I transfer a file, that is, drag and drop from my computer to another computer, the router loses connection to the Internet. The internal network is fine, but I have to reset the router to reconnect to the Internet. Why is it doing this?
Basically, you just have buggy equipment. There's no good reason for that to happen. Make sure you have the latest firmware on your router and the latest wireless drivers on your computers.
If you have truly isolated the problem to the router, replace it with a higher quality router.