However here is my probleme;

my SD card was working bad on my camera, so i formated it, however now its 100% empty.

do i need to install something to it to make it work again cuz when i put it back it simply act like if i did nothing.

Normally what happens when you format things is that it erases everything. What was the intended result you were seeking?

yes however there was some folder in the card ( i guess the driver for the card ? i dunno )

when the card had no picture on it it was still left say 25% used ( its a 2GB )

however not its 100% empty.

Is the card working with your camera?

Formatting it will erase everything.