Proxy question

Alright guys,

Probably a dumb ass question about proxies but I'll ask anyhow.

I understand the main gist of the proxy. You use one to mask your real IP to places that you visit, etc...

The question I have is can your ISP detect the proxy change or do they even care?

I'm not sure the exact answer to that but I think your ISP sometimes randomly checks what you download (at least they have in my case) and they can only know what you download if you are using your IP. If you are using a different IP I don't think they can find out. I downloaded a cd a couple of years ago and my ISP sent a "warning" letter to my address! Ever since, I have been using proxies for downloading and I don't get any more of those warning letters lol.