IIS6 custom asp.net 404 page

[Guest]

I've setup a custom 404 error page for my asp.net site. I have configured IIS
to process non aspx pages and also added the correct web.config custom error
section to the applicaiton. Every thing is working as expected expect with
aspx pages.

I get the bad page url in the aspxerrorpath querystring but it doesn't
contain the original querystring . All non aspx page pass the original
querystring to the custom 404 page.
I need to have access to the original 'id' querystring parameter in both
cases below
ex.
http://data-architech.net/testpage.htm?id=1 - this works
http://data-architech.net/testpage.aspx?id=1 - this doen't

Any Help please??

 

[Guest]

OK if I go to IIS config and in the app ext mappings config , I check verify
that file exists for aspx extenstion THEN I get the query string just like a
bad (404) html request.
Is the the correct way to handle this.
What are the performace implicaitons of verifing that aspx files exist from
IIS?
Looking for some confirmation that this is not creating a performace bottle
neck for the site.