Can't remove split

Question

I have one computer with windows 8.1 and Office 2013 that I do most of my work on, but I sometimes switch to a really old Vista computer with OpenOffice when I'm traveling. Whenever I switch a file from one program to the other, all of the row and column headings disappear (i.e.: A, B, C...), and Excel thinks that the file is split. It seems the only way I can get the headings back is to remove the split. But, whenever I highlight everything in the document (I do either ctrl+shift+end from the beginning or ctrl+a twice) and click "split", the split won't go away. It still thinks the document is split. And no matter how many times I click split or try different things, it still tells me it's split. Does anyone know how to fix this?