Getting short (DOS) name of file?

I'm trying to run some (often user-defined) files on my windows server. Thing is, it seems to want short names (like C:\PROGRA~1\WHATEVER\PROG.EXE). Is there any way to get the short name from a long name? -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.