|First try to rename file. Go to tools, folder options, file types and check have you .xlsx extension. If not then rename the file .xlsx to .xls|
Second try to use excel command in file menu – Open and Repair. File, open, select the corrupted file and click open and repair option.
Another recommended solution: if you was unable to resolve this problem through above steps then you should try any third-party software. There are a lot of them on the internet, both free or pay versions.
Also you can find more information here: http://www.ask.com/answers/616743761/problem-opening-a-xls-file?qsrc=14106/
And good luck!