sudo modprobe -r ath5k
sudo modprobe acer_wmi
sudo modprobe ath5k 

On a Medion MD97600 laptop the commands for enabiling WIFI are a bit different: Read the original site here in French

first you should install som drivers:

now enter these commands in a textfile

modprobe acerhk

echo 1 > /proc/driver/acerhk/wirelessled

I gave it the name wifi-on.sh

---

make it executable. (e.g. bij setting the rights with nautilus)




Enter ALT F2 and enter: gksu gedit /etc/sudoers  and press enter.

and in the file that opens, add to the very last line (replacing "username" with your login name):
-------------------------------------------------------------------
username ALL= NOPASSWD: scriptpath
-------------------------------------------------------------------
BE SURE TO REPLACE "username" WITH YOUR LOGIN NAME.
and replace scriptpath with the path to the file you want to run without a password.

for example, I want the script to run at startup as sudo without typing in the password. The last line in my file looks like:

jeroen ALL= NOPASSWD: /home/jeroen/wifi-on.sh

where "jeroen" is my user name and "/home/jeroen/wifi-on.sh" is the script i want to run.

now save the file and close it. you are now allowed to run your script as sudo without typing in a password.

so go to system > preferences > sessions and add the command you want to run at startup under "startup programs", mine looks like:
gksu /home/jeroen/wifi-on.sh (replacing the path with the path to your script).

Reboot and configure your Wifi.
Reboot again and the machine should go online automatically. Even better than Windows Vista does.