Addtional URLs with .html extension not working

I need some help here. I migrated a static website to Sitefinity ver. 6.3 in my local machine running in IIS7. I added mulitple urls on each pages and it works fine, all pages are accessible through the additional urls. The problem is when i migrated it to our test server that is running in IIS6, i got 404 page whenever I access the pages using their additional urls that has html extension. Can you give me some advice here? Thanks in advance!