IIRC, NT doesn't have the concept of "long" and "short" names. Check on this with windows explorer -- right-click a file, and see if it gives you a long and short name.

If it doesn't, what you're asking for is simply impossible. If it does, look at Win32::API, and search on Microsoft Developer Network for the proper API function to call. IIRC, there's a fairly simple API for this.