Thanks for the quick answers!
I tried the hdwwiz method, but when I changed the driver, it still didn't want to take the driver (I got something about the driver not being compatible with my device). I'm running Win7 in 64 bits, does this could be the reason? (i.e. no atmel dfu driver for win7 64bits?)
For your informations, the informations about the driver in the device manager are as follow:
Driver Provider: http://www.arduino.cc
Driver Date: 15/11/2007
Driver Version: 5.1.2600.0
Digital Signer: Not digitally signed
And the setting for the port are those:
Bits per second: 115200
Data bits: 8
Stop bits: 1
Flow control: None
No luck apparently!