Beside all the solutions, what I would proposed,
I assume what you would want is, you have a Default.aspx page when you woould run the site Default.aspx will be displaying as ABCXYZ.aspx in the address bar and also
YOU ARE NOT mentioning physical renaming of the default.aspx to ABCXYZ.aspx.
If I am correct then you might need to consider URL rewriting in ASP.NET, please a have a look following site,
URL Rewriting in ASP.NET[
^]
Hope it helps :)