Although it is usually more efficient to use a Dynamic Link Library (DLL) that meshes well with the Internet Information Server (IIS) and Active Server Pages (ASP) environment, you may just need to run an old DOS application via an ASP page. Stephen Genusa offers just such a component that lets you execute DOS and Windows applications. The results are returned as a string. You can get the component at this address:
What's even better, Stephen offers the ASPExec component for free.