yes thats what i mean.
why is it a bad idea?
this drive is using for data files (documents, music etc..)
It makes ongoing maintenance much harder.
Need to reinstall the OS? Pain.
Need to replace one of the drives, for whatever reason? Pain.
Safety considerations.
If one drive dies, all data across both drives is lost.
Makes managing backups much more difficult. (you ARE doing backups, right? hint hint)
Solution:
Just get another drive. Start using that for docs/music/games/whatever.
What, specifically, is taking up that 2TB? If games, and especially Steam games, it is trivially easy to move that to a new drive.