Application installed for All Users

I have an C# windows application that is often installed on a Terminal Server.

The person installing it can install it for 'All Users', or just 'This User'.

I need to store and retrieve things from the registry depending on whether the app was installed for All users or not.

How do I find this out in code?

Store a field in the registry with how it was installed? Or create a file on installation containing which method was used.

It's totally down to personal preference (There are of course more ways, they're just the two I'd fight with).