Hello I am planning to upgrade my website from classic ASP to ASP.NET however all external sites link to my .ASP pages. I would like to maintain those backlinks Is there any solution to this problem? If there is a way to make a windows server interpret a page with a .asp extension as an aspx page that would be nifty.
Your best friend according to the SEO world is 301 redirects. 301 redirects are the best way in relocating pages. Every URL that used to point to a old asp page should be replaced with a 301 (Resource permanently relocated) redirect to the new ASP.NET page. You can google ways of implementing redirects but this is ussually done in your .htaccess file as redirect 301 oldURL newURL
htaccess are for Apache. If you're using IIS, you can use an HttpModule. http://ravi-testingblog.blogspot.com/2009/07/how-to-create-your-own-http-module.html is a guide on how to do it. From there you can add a BeginRequest event which checks if the requested page is an ASP and redirect it accordingly. From there you can do full Url rewrites to make your pages even more SEO friendly.