Excel keeps converting numbers to dates on copy/paste

This has been a problem for as long as I have used Excel (years and years and years). Many times when I copy/paste numbers into Excel, the program will autoconvert the number to a date to something like May-99 and the actually value in the cell is changed as well to like 05/05/1999 ... how to keep it from autoconverting? As well as the autoconverting to scientific notation. This refers to my previous question about validating serial numbers in another post. I might have a serial number I am copy/pasting into a spreadsheet like 39579312003003 ... that will be autoconverted to scientific notation. annoying.

Thanks.

Also...how can I force Excel to not drop leading zeros in a copy/paste....these serial numbers might begin with a few zeros. Would be nice for them to not be dropped....so basically with all this is there a way to format a blank spreadsheet to not autoconvert to dates, nor autoconvert to scientific, nor drop leading zeros before I paste data?

Thanks.

If you type a apostrophe before your number it will leave it alone, and not autoconvert. That will at least help on the smaller scale. I don't know of anyway around it for a mass copy/paste.

That will also preserve any "0" you have in front of a number.