file download c# asp.net

I need help on this.

In my project I have a folder called "files". Inside that folder I have many file which I have uploaded. Now ,just by writing the link of the files in the address bar of Web Browser (ex: http://localhost:1234/Server/files/file.rar) anyone can download that file. I want to change that. When the clients are writing the link, instead of downloading the file, another page will be opened (ex: continue.aspx) and by clicking a button on that page, they can download that file (the story is like in rapidshare, filefactory, megaupload ...)

Can anyone tell how this can be done.