If you've got the previous version feature enabled, just right-click the file -> properties -> Previous versions. There click the previous version and click open to verify it is the right one, then restore.
If you haven't enabled this feature... Well the odds of hetting that file back are kinda low (depending on how much you write to the disk). NOW DO NOT INSTALL OR WRITE ANYTHING to the disk the file is on. If the original file didn't get overwritten by anything (it is possible the new version got written somewhere else on the disk), it should still be there, just not visible by the system.
Try one of the file recovery utilities like DataRecovery http://tokiwa.qee.jp/EN/dr.html (just download it onto another drive). If all fails, you are probably out of luck. You could try one of the local file recovery companies (the really expensive ones who physically disassemble the hdd in order to get to the data that was there.) if the data is REALLY important.