After several manual Nvidia driver installations folder C:\Program Files\NVIDIA Corporation\Installer2 grew up to 2.7 Gb
Judging by subfolders date it contains all the previous versions of drivers data.
I suppose removing all the folders except the ones with the latest date should be safe. Except InstallerCore folder - it has old date, but new files.
Or maybe remove all the files with the old date and then remove all empty folders.