Companies absolutely run Windows servers. In fact, every single company I've ever worked for (except one very small company) has had them. Usually at a minimum, you will have servers running Active Directory, and perhaps DNS (because AD-integrated DNS zones are useful). Then, more often than not companies are MS Exchange shops, plus Sharepoint is common enough.

Generally people aren't running web servers on Windows, but the internal IT infrastructure world uses a ton of Windows servers.

windows sysadmins are very much a thing. desktop and laptop MS Windows installed in any company doing anything important is sysadmin'ed centrally. If you require security (not to leak company info) you must disable the ability for users to install anything. The side benefit of this is that the admins can admin other things like mail servers, ip addresses, etc. My gf (accountant) has to call the sysadmins to plug in an external display at home, which they can do remotely at 2 in the morning.

> Do companies run windows on servers?

All of the Fortune 500 probably does.