I want to uninstall and reinstall oblivion so ALL my mods go away, because I have some messed up mods in there and whatnot...so i uninstall and reinstall it, but all my mods are still there, including ones iv made myself in the construction set. When i uninstalled oblivion i checked if oblivion's file was still there, and its not so it is completely out of my system. How do i make them all go away?

Not sure what OS you're using, but for Windows 7 (64 bit) what *I* do is to uninstall anything like DLC (e.g., Knights of the Nine) first, then Oblivion itself. Then I also delete the Oblivion directory (where the game was installed), along with My Documents\My Games\Oblivion and Users\[Username Goes Here]\AppData\Local\Oblivion - note that AppData is normally Hidden. Well it is even now, for me, but I can view those files because I chose to be able to do so in the Windows folders options.

That's it. And, I suspect, you would only really need to do all of that except for the AppData bit - probably not necessary, but I'm fussy/odd like that.

Often uninstalling something does not delete everything; especially if those files are not installed together, rather added later by user. Uninstalling Oblivion does not delete any mods you installed, and nor saves you made. If you want to delete your mods as well, you have to delete \Data manually. But if you have enough HDD space, rename it instead of delete it. Then reinstall your game, install mod one by one, until you don't need old data directory anymore.

Use Revo Uninstaller (http://www.revouninstaller.com/revo_uninstaller_free_download.html) to uninstall everything, including all Registry Entries.

Uninstall all DLCs, CS and Oblivion itself - also, you don't have two installs o Oblivion on your PC, do you? Make sure you uninstall everythign Oblivion related using Revo above. Then go and delete the Data folder where Oblivion was installed. As your mods are not part of Oblivion, they are not getting uninstalled and are still in the same Data folder you installed Oblivion to, and where you are reinstalling. Restart your PC after deleting the data folder (back it up if you want to), and then reinstall Oblivion, preferable in a different location (C:\Games\Bethesda Softworks\Oblivion).

Should work out fine.

http://tesnexus.com/downloads/file.php?id=20258

The game's installer will only remove files that it added in the first place, it won't touch anything that you've put into the Data folder yourself. You just need to do that manually after removing Oblivion.