Putting an aspx website within another aspx website's root directory

I have translated a company's website to English, the aspx webpages have a masterpage.

So, the structure is like this

Server/Website's Root Folder/ ---> This directory has the webpages in their native language.

Server/Website's Root Folder/en/ ---> This directory has the webpages in the english language. Also renamed the company.master to company_en.master and changed the references to the masterpage.

Now, when I type the url www.company.com it runs fine.

Once ı try to access www.company.com/en I get a runtime error saying;

Server Error in '/' Application.

Is it possible to do this or should I get a new domain name?