Why is my internet all of a sudden so slow?

I have an ASUS. Win 7. I have wifi connection in the building.

My internet connection is very slow all of a sudden.
I already restored my computer for one week ago.
I uninstalled and reinstalled the wifi device.
Antivirus and anti spyware says it's all fine.
Already changed my IPV4 dns for 8.8.8.8.
Already tried with ultrasurf on and off.
Already erased cookies, cache, history bla bla bla.
Other laptops with the same wifi connection at the same time in the same location work just fine.
Any ideas?