.lst files are basic text files so can be viewed in any test viewer/editor (Notepad, wordpad, Viewer etc). SAS also comes with a separate file viewer called SAS View which opens List and Log files and can be told to highlight keywords (Like Note, Warning and Error in Log files) and can also be used to view datasets. I heartily recommend using that one if you can get your hands on it. I believe it's an optional component when you install SAS.