I am trying to uninstall Dawnguard from my computer but I was unsure if I could just delete the data file in the Data folder or if there was other files I had to uninstall with it. I don't seem to be able to uninstall through Steam or anything. I just wanted to make sure everything from Dawnguard would be deleted properly before I go tamper with anything. Any help will be greatly appreciated.

You can simply deactivate Dawnguard.esm in your Skyrim launcher and then make a new character.

I would imagine if you delete the Danwguard.esm and Dawnguard.bsa files, your system will probably download them again whenever there is a Skyrim update, since your account is linked to the DLC.

Great, thank you very much!