FINALLY my computer works again. GOD it took an eternity to get the right things installed and to work properly.
I originally wanted to install Windows XP, but couldn't find my CD, tried it with older versions but the drivers for literally everything didn't work there, so I installed W7 again (I didn't want that at first, because my Computer is old and I thought maybe everything would work better if I use XP again...)

So, meh... As long as everything i need works, it's fine