What is causing it to sort?
Do you have a script trigger such as onLayoutEnter performing a script that sorts the records?
What version of FileMaker do you have?
Sorry, forgot to say... am using FM 12 Adv. I have no triggers set. I simply imported a table from an Excel file as it was, now, anytime I open that FM table it automatically sorts on the Account Ref field which happens to be the first field also. I've looked and can't find anything to say 'sort on...' or similar.
Go to the layout, select Sort from the sort menu.
Either specify "unsort" or clear the "keep records in sorted order" check box.