You open the photo in windows using "windows picture and fax viewer". You click on the printer icon, you see the image printing wizard, click next, then go to printing preferences, then the advanced tab and there you need to enable the option of printing a poster (you choose how many A4 sheets you want to make, click ok and then continue on until it starts printing).
* found on the internet
And in new windows (7 and above) it may look like this:
Right click on the image file and select "Print". The "Image Printing" wizard starts. Click "Options", then "Printer Properties". In the "Configuration" tab you find "finishing mode" and from the drop-down list select "Poster printing" and in the options you choose how many pages you want (max 4x4).
Fast, efficient, requires minimal knowledge and no graphics processing programs. Alternatively, you can also hide behind the lack of sufficient information ("You just beat everyone !!!") and be offended because something.

Mother, how did you make my day, anmedia. :)
EDIT:
If in the printer options it can't be done, it's done like this:
You download and install PDF Creator. You print an image, but choose PDF Creator as the printer and choose A2 as the paper size. You open the pdf file in Adobe Reader, click print, in the "Size and page handling" section, select "poster", and set the scale of the fragment to 94%. You are already printing to a physical printer. And voila.