You will need to reinstall windows. Backup your data and you won't lose anything. If you're using the integrated GPU, then IDK what GPU software you're referring to, but yes, it will probably be useless. Your HDD will not be harmed by reinstalling Windows, just be sure to backup your data. Even if you don't, you shouldn't lose anything, but it is a good habit to get into since you never know when something can go wrong.
Assuming you don't reformat during the install, all of your old data will be automatically moved to this folder without the quotation marks during the reinstall:
"C:/Windows.old"