Can I still run ASP pages on a server that runs ASP.Net?

Yes, you may run ASP pages on a server that runs ASP.NET.

Microsoft Active Server Pages (ASP) is a server-side scripting environment that you can use to create and run dynamic, interactive Web server applications. With ASP, you can combine HTML pages, script commands, and COM components to create interactive web pages or powerful web-based applications, which are easy to develop and modify.

ASP.NET is a programming framework built on the common language runtime that can be used on a server to build powerful web applications. Both ASP and ASP.NET applications can run side by side on a server without adversely affecting each other. This is primarily due to the fact that separate file extensions (.asp versus .aspx) and separate configuration models (metabase/registry versus XML-based configuration files) are used between the two technologies. The two systems have totally separate processing engines.

It is possible to have part of one application running ASP and another part of the same application running ASP.NET. This is very beneficial if you need to move a large, rapidly changing site to ASP.NET one piece at a time. Additionally, if you are going to move to ASP.NET, you may want to use this compatibility to make as many architectural and design improvements as you can. For these types of situations, coexistence using a phased-in approach is an absolute must.