If all you did was pick the file (in the "File Open" dialog), and you didn't "save it" in the Piping Input Processor, then the format of the input hasn't changed and you can get the file back. Do this (carefully):

- Enter the input (in Version 5.00) for the job in question.
- While the input is open, use Windows Explorer to copy the ._A file to a different directory.
- After the copy, close the 5.00 input.
- You should now be able to start Version 4.50, navigate to the 4.50 data directory and enter the input for the job.

If you have saved the input in Version 5.00, it may not be possible to go back to Version 4.50. If this is the case, I'd suggest sending the .CAESAR II file to us so we can attempt this for you.