SureAI

I reinstalled 2 times yesterday.. And i don't have steam..

did you reinstall Skyrim as well?
also, "from a newly downloaded installation package"?
yours likely got corrupted; use the torrent option to be safe

Here you will find a detailed installation guide.

It is easier to install Steam.
You get a Skyrim Classic Edition Steam key from the official site here.
A little cheaper here.

You probably have Skyrim 1.00?
But you need the latest version of Skyrim 1.9.32, so you need an update via Steam. (also on the Skyrim DVD or online)
To do this, you must install Steam, create an account, register, and update Skyrim.
The Skyrim key should be on your Skyrim DVD.
Only then can you install Enderal (and then update)
And then you can play Enderal.
Of course your Skyrim should be legal.