Decimal vs. Thousands Separator

I import an array of data from a text document to Excel; the array contains only numbers.
The problem is that if a number has exactly three digits after the decimal the decimal separator is considered to be a thousands separator; thus 1.446 (one point four four six) becomes 1446 (one thousand four hundred forty six.

Control panels regional and language options is set to decimal comma and point for thousands separator and that is fixed as it is a company owned computer with only IT-dept. access to such things. However, Excel operates with decimal point. I don't know this is set up.

NSV