How do I install Polish language in Windows 7?

Hello. I had Windows 7 Home Premium on my other laptop, but my SSD broke down suddelny, so I purchased new SSD and installed same Windows 7 Home Premium found on the internet (Microsoft website won't let me download installation file, which is hilarious in my opinion...). Now I installed it and activated online with the same key code I got on my Microsoft Windows security label sticked under laptop. But this is English version only and I need to have Polish language (not only keybord, but the whole system). Trying to do so, I found below message and the "Support" window says I can't download my native language. Why is that? How can I solve it? I got original, legal system from the very beginning and I'm not going to buy new one only because I can't download it from MS website and I don't have original installation file.