patching Oblivion with 1.2.0461...
 

Yeah I tried to patch Oblivion to the latest version and I got error report: "Old file cannot be found,... blah blah" or something, you know how it goes...
Then I tried to patch it with the previous version patch (1.1.511), which worked last time, but there was error again.

What do I do if I want the newest patch installed?

you surely grabbed the wrong update (or language version).
check your version in the game menu and search for the patch on the games website.

Probably cause you used a crack it cant find the old protected file therefor wont update.

yep thats another reason, Oblivion uses the RichTIme Patcher wich updates original files only (crc checking).

Yeah that's it. Because it's the right version, I'm (almost) sure.

Then how do I update??

Re-install the game and run the update again.

I did and it works. Thanks.