That's a server limitation that you'll have to ask your host about. 2mb is usually the default for uploads using http protocol under iis. It can be overrided but maybe only on a server-wide basis IIRC.
You should look into using ftp for uploading files larger than 2mb as ftp is uses a lot fewer server resources than http.
There is at least one upload component out there that supports files larger than 2mb via http, I forget what it is, but it's not one of the more common ones. Your host would know about it if they support it.