Delete Thousands of Extra Columns

I think I know what happened here. She accidentally copied the contents of a cell into entire rows instead of an appropriate selection.

I'm curious as to how to fix this "cleanly" as well.

Here's a sample book. You want the EXTRA columns to go away and have the sheet go back to your standard A-Z or whatever without the huge blank space screwing up your horizontal scroll bar, right?

Extra column sample book.xlsx

That is spot on. Yes, I am trying to have it go back to standard and eliminate the hassle of scrolling over too far into the blank columns. Let me know if you can think of anything. I tried a number of common sense type solutions (I used excel in college, but nothing more advanced than that), nothing worked except for hiding them, which is my current fix.

I spoke too soon, found another way.

Select the extra columns, right-click-> Delete, then immediately save the document, close it and re-open it.

Great! The immediate save worked, thanks!