iCloud isn't downloading photos to my Windows 8 PC. How to fix?

I've had an iPad for two years and an iPhone for a year. Between the two I haven't been able to successfully download any photos outside of the painstaking process of emailing them to myself or going into the icloud website, and downloading the moments, bit by bit. In that process I seem to be missing about a years worth of photos which distinctly *****! Outside of that however, I am trying to download the photos through the update to iTunes with iCloud. The program has downloaded fine but I can't get the photos to all upload onto my computer successfully.