You guys can put an end to these type of headaches by just creating a new partition on your shiny-new, big-capacity hard drives and use it exclusively for sims and games. If you're not sure how, just take the rigs back to the geek department of the store from which you purchased and ask for help with software tool choices and other do-it-yourself advice, or just pay them to do it for you. Putting all of your fav games and sims on another partition drive or another internal hard drive is the best way to get these newfangled Windows OS's to stop interfering so much. Its still useful to turn off UAC when possible and use compatibility choices when applicable, but from a security standpoint, these newer systems like Seven and Eight also behave entirely different to mod work done to programs on drives other than the system drive -- they just don't care.
The other benefit is that if your system drive gets FUBAR for whatever reason and you have to wipe it and reinstall the system, your customized favs are spared from any data loss. You may find that you need to have registry entries for these programs in the system registry in order to install many payware addons. If this is your situation, you rename the old sim folders on the other drive to whatever, reinstall the sims again with their original folder names, rename these newly installed sim folders to something else, then rename the old folders back to their original names and delete the new sim folders with Shift+Delete for permanent wipe. What this does is protect your old stuff from being overwritten during program re-installation while the system creates their new registry entries.