Do what Oracle is telling you to do...

1- Check if you actually have a valid parameter file on C:/WINNT/TEMP/2892120138.dat
2- If you have any doubts ask Oracle for help e.g. exp help=y

What happens if you run the export manually?

Don't forget to read error messages and documentation carefully, I know for a fact you don't do that because of you have posted your question in the wrong section of the forum.