After I downloaded a mod that made the game crash, I uninstalled Oblivion, figuring that if I reinstalled it, everything would be back to normal.
However, I've reinstalled it twice now, and every time I get to the loading screen before the main menu. There are no mods at all in the Data file,
but the meshes, misc, sounds, textures, voices 1 and 2 files are somehow in a compressed WinRAR format (pile of purple, green and blue books icon).
Is this normal? I've considered downloading a program that will completely erase Oblivion, but maybe someone here has a better understanding of computers than me.
Thanks in advance for any help given.

Back up your saves. (My Games\Oblivion\Saves)

Uninstall the game.

Delete the oblivion folder in My Games, AND the folder in C:\Program Files\Bethesda Softworks.

Empty recycle bin.

Reboot.

Reinstall the game OUTSIDE the program files folder. (C:\Games\Oblivion would be good.)

Play.

Thanks, the game is working again.
However, the texture, meshes , etc. files are still compressed for some reason, and I think I can't do mods because of that; I tried the arrive by ship mod, but it changes nothing to the game.