Okay! So! I've made a BIT of progress. I've downloaded, uninstalled, and re-downloaded this so many times.. I temporarily took down my firewall as well as put it as an acception before that. It'll extract, and then it'll decompress... but after that, the Windows Installer pops up with that error... Does anyone know what this could be? Thank you SO much, and I'm sorry in advanced for being stupid.
It sounds like your antivirus is interfering with the download process. Try keeping your antivirus disabled through the download and installation process.
Alternatively you could download the files manually without an installation package, if you are unable to resolve your issues. See this guide I created. http://royals.ms/forum/threads/mapleroyals-manual-install.19701/