The virtual path '/Products2.aspx' maps to another application, which is not allowed.

I have a web app that starts at the page http://localhost/Dev/Products2.aspx
 In Products2.aspx, I have two links, Books.aspx and DVDS.aspx.
 When the user clicks on the Books.aspx link, I want to rewrite the path to "/Products2.aspx?Category=Books", but when I do this, I get the following error in the Application_BeginRequest Method in the Global.asax file:
 The virtual path '/Products2.aspx' maps to another application, which is not allowed. 

Here is the code for the Application_BeginRequest:
 
1 void Application_BeginRequest(object sender, EventArgs e)
2 {
3 string fullOriginalpath = Request.Url.ToString();
4
5 if (fullOriginalpath.Contains("/Pro ...