Legacy Update lets you get your Windows 7 install updated to the latest patches / security fixes Microsoft released.

https://legacyupdate.net

When installing Windows 7 on ProxMox, there is a device that won't accept the VirtIO Serial drivers (vioserial folder) until this update to Windows is applied.  See the detailed description for links to forum threads that explain the situation and how to install the update from the .cab file that is in this archive.  Also links to get this file right from Microsoft, but I'm guessing the Microsoft links won't be valid much longer, that is why I'm posting this here.  Updates in this archive are for both x64 & x86.