How can I close my currently open Excel without it saving ?

Hi
Office 2010,
I have just seen excel place columns B to N into A wiping out all the text for the transactions whose prices were in B onwards, which were headed Jan to Dec in B to M and the totals in N.

It would be stupid to close Excel as it would save that, as it is, unless it is saving as I work Excel (is it ?) in which case I am nuked, I need to close Excel without it saving everything I did and it did without me wanting what it did, open it (the good one) up again to see that page before this happened.

Furthermore what happened there ?
All I did was paste the text from row 20 into row 21 then I couldnt get rid of the 'crawling ants' so I hit esc, nothing, clicked another sheet, then went back and A had then received B C D etc all stuffed into A ! A is in fact now made up of columns, so at the very top is a wide grey cell A, next row says Subject, below that are columns with data from B onwards which still exists beyond the dark line at RHGS edge of A.
If I click in the first of these columns that selected cell also at the same time is also selected in B, and as I tab right, I am seeing double selections, so its mirroring the columns B C etc in A !

I clicked undo but no joy.

I will keep excel minimised to taskbar until someone can help.

I recall having this happen once before and had to research and rebuild an entire page again, took the entire day.

What I do want to set up after getting out of this pickle is to STOP Excel saving without me wishing it, during use and when closing, as in all other progs I DECIDE TO SAVE, I do Ctrl S every so often when I am happy with what I want to save, else a prog can save the actions of a gremlin !

Is there some place that incremental saves get made to during using Excel 2010, maybe I can look through those if there is no other way to get out of this pickle.

Also I seem to have a limited number of undos, 2 and that was that, can I extend the number in preferences or would there have been more but the gremlin has denied me undoing its actions ?

Thanks
DBenz