I can't view most of my photos i've downloaded from my icloud onto my windows laptop

All these years, I have downloaded my photos from my icloud onto my windows laptop, and have never had a problem with viewing them. For the past year, I've not been able to view my pictures because I need to download an extension I've never needed before. The extension costs money I don't want to spend because I've never had to buy it before and I've just read online that these pictures can be viewed on ipads or macs without buying the extension. Has anyone else had this problem and been able to sort it out?