JD_Toims - 4:02 am on Jul 23, 2013 (gmt 0)
The left side of your rule was fine initially, except for the unescaped . (dot) -- (It should be: ^Login\.aspx$). The right side is still incorrect -- (The right side should be an absolute URL for a redirect, meaning it should start with http:). If you need to match the exact query_string (stuff after the ?) you're posting you'll need to use a condition.
There are some tutorials at the bottom of the page in the Library [webmasterworld.com] that should help you understand more about rewriting and redirecting.