Update: a very good free website that generates high quality barcodes for you: http://www.terryburton.co.uk/barcodewriter/generator/
Update: if you require some sort of Windows automatization (e.g. in Excel), check out Auto It programming language for writing scripts : http://www.autoitscript.com/site/autoit/

The EAN-13 barcodes are used worldwide for marking products often sold at retail point of sale (for example books, etc). I recently found this free EAN-13 barcode making way (requires Microsoft Excel or similar), which I want to show below. First you need to download this archive that contains two files: EAN13.xls and ean13.ttf.

After you have downloaded and unzipped these files, right click on the ean13.ttf and click Install.

Then open EAN13.xls file in Microsoft Excel, and click Enable Macros (it will not work if macros are disabled!).

 

Now you can create your own barcodes, just by replacing the numbers with yours. Remember, you only need to enter first 11 digits of your code, the last one is a check digit and is calculated automatically. 

If you want to paste this code directly into a word processing program, just right click the cell with the barcode, and copy it, open your word processor and paste it there. 

Or alternatively, zoom in on the cell with barcode in excel, and press Print Screen button on your keyboard. And then crop the screenshot in any image editor. This will give you a high-resolution picture of you barcode.

Alternatively you can use this program to generate the barcode for you.