No, once your history is gone, you can't access it.
DAT files can't necesarily be opened in one particular program. They are just used by other programs to hold data, if that makes sense. However, many times you can open them in notepad and be able to see 'some' of the contents. Just right-click on the .dat file and go to Open With, select Notepad and hit OK.
Again, you'll be able to view 'some' of the content, but the vast, vast majority will seem like garbage to you. DON'T make changes to the file, though. You could cause problems by doing so.