Every other time you run the USGS MP Metadata Translator with anything except XML files, the tool will fail with the error "The process cannot access the file 'C:\Documents and Settings\aleta\Local Settings\Temp\translator_source.xml' because it is being used by another process."
When running the USGS MP Metadata Translator tool, keep the geoprocessing Command Line Window open. If the tool fails you will be able to copy the last command that was run and re-execute it in the Command Line Window. After the second time you execute the command it will be successful. This avoids having to open the tool again and redefine the arguments again manually.