I recently started usind the creation kit for Oblivion but any mod I make do not appear in-game,
I've tried running it as Administrator and I've disabled the UAC but nothing works.

I would really appreciate any help that can be provided, thanks.

Did you remember to enable it in the game launcher (or whatever mod manager you use)?

If it is not in the list, the esp file may have been saved in C:\Users\\AppData\Local\VirtualStore\Program Files\ (on W7, I don't know the path on Vista).

Did you put the mod in the Data folder in the game directory? Did you check the mod in the launcher before you launch the game?

It's saved in the data folder and checked in the launcher, I've made mods for Fallout 3, New Vegas and Skyrim all with no problem, only Oblivion seems to have the problem.

I seem to remember an annoying bug in Oblivion where the launcher would clear the selection when the list of data files were displayed. Try to go to your C:\Users\\AppData\Local\Oblivion folder and open the plugins.txt file. Your mod should be in the list. If it is not, add it and start the game.