Hello. I currently have Skyrim SE purchased thru Steam on my E drive under Steam. I've been playing around with it and now I want to uninstall it completely so I can reinstall it again, hopefully correctly this time. As this game is on the E drive I know that I can just hit delete to remove those files. But will this remove it completely? What about registry entries, etc? I'm still using Windows 7. Once I get it removed completely, what is the best way to install/reinstall it? I know this sounds like a pretty stupid question, but I want to add some mods and I want to get it right. As always, your help is greatly appreciated.

No. Anything outside the main file folder will be left behind, including not only registry entries, but also saved games and/or game settings that were stored in the hidden AppData folder on the C: drive. And if you have "Steam Cloud" active anything the Steam server has collected will remain there.

Is there some reason you can't remove the game using the Programs icon in Control Panel?
Or use Steam Client to remove the game.
Open Steam Client and log in
Library tab
Right-click game and choose Uninstall.
Confirm the uninstall.