Which operative are you running on your pc?
Do you have admin rights on the computer you are using?
It could be a faulty download or install. Maybe try to download and install again, but uninstall the current version first - and reboot.
If that doesn't work, try running VSD as an admin (right-click on the icon and choose run as admin).
BTW, I hope you are aware that Visual Site Designer (VSD) is a different programme from Responsive Site Designer (RSD), which is the one mentioned earlier in the other thread you posted in. If you want to have a responsive website that can be viewed on all sorts of screen sizes, I'd go for the latter.