ANSWER:

My solution:
I’ve got the same issue with importing serial numbers.
They don’t have to be treated as numbers, ie no mathematical functions are performed on it, but we need the entire number in there.
The simplest thing I have is to insert a space in the serial number.
eg “12345678 90123456 1234″.
When Excel imports it, it will be treated as text instead of a numeric.

by Peterlip from http://superuser.com/questions/421886