I lost my SkyrimPrefs.ini file, and now i don't have any, from where i can get one ?

reinstall.
Or maybe a very friendly guy here will provide one for you.

Make sure you backup your saves before you reinstall!

Just rename it, launch the launcher and it will create a new one. No?

Oh, this could work, actually. Silly me.

Aside from that, in the Skyrim folder under Steamapps>Common, there are four pre-configured .ini files: Low, Medium, High, and Very High. Just copy and paste the one you want in the Skyrim folder in My Games and rename it to skyrimPrefs.ini

If you don't plan on reusing t don't rename it. Just delete it(and the other one if you want. Start the game and redo your graphics options.

And if you are missing any inis from the steam installation folder, you don't have to reinstall, you can verify the integrity of game cache (Skyrim->properties->local files->verify..) Steam will download any missing files.

i can post it in here in a bit. Im downloading the game on my office (shhhhhhhhhhh) pc and i can copy/paste the ini files here in their untouched form.