Out of all the computers, I've built I've always used a separate hard disk drive or solid state drive to separate the contents of the operating system and the user files. However, eventually somehow someway user folders even not knowingly will have content on the operating system drive. Throughout the years, I've discovered little tricks to OPT content out of that drive such as switching all download directories. Automatic downloads to certain drives. So I was wondering, have anyone found a for sure thing that works or, just nit pick things that will improve the chances of nothing ending up on that drive. Also, the operating system is mainly Windows. More specifically Windows 10.
Depending on your operating system you can set the automatic download locations for all your music, videos, documents, downloads etc for windows 10 and the file explorer.
Otherwise it just takes a careful eye when installing things to actually pause and read the path that you're installing or extracting things too. Also changing the library locations is very easy to do on all versions of windows.
You are right occasionally the misc file gets transferred to the OS drive accidentally, but this wont cause much of an issue in the long run. Simply watch your path destinations and you will be fine.
You can also simply change the registry file that sets the default file path for installations: