Why IIRF doesn't rewrite rules for .asp files?

I have Windows Server 2003, I开发者_StackOverflow中文版IS6 with IIRF installed on it. And I have iirf.ini file as follows:

RewriteEngine ON
RewriteLog c:\inetpub\iirfLogs\iirf
RewriteLogLevel 1
StatusInquiry ON
CondSubstringBackrefFlag *

RewriteRule ^/(.*)$       /index.php?p=$1 [U,L]

And it works fine for all the requests except those that ends with .asp (example mysite.com/123.asp). That's why all the requests for .asp files gives me 404 error.

How to fix this bug?