eth1 interface wakes up after sudo ifconfig eth1 down

Since few days, when I turn on my laptop (Dell Inspiron 6000), I have eth0 & eth1 active at boot, but only eth0 is used, eth1 is the wifi card, and I don't use it.

So, I do a "sudo ifconfig eth1 down", but less than a minute later, eth1 has woke up.

But when I check just after typing the command, eth1 doesn't appears, so she's inactive, and she turns on without any human action.

For help, I give you my /etc/network/interfaces, and my ifconfig with eth0 and eth1 up.

/etc/network/interfaces :

root@essendon:/# cat /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.0.2
netmask 255.255.255.0
gateway 192.168.0.1

#auto eth1
#iface eth1 inet dhcp

#auto eth2
#iface eth2 inet dhcp

#auto ath0
#iface ath0 inet dhcp

#auto wlan0
#iface wlan0 inet dhcp

ifconfig with eth0 and eth1 up :

root@essendon:/etc# ifconfig
eth0 Lien encap:Ethernet HWaddr 00:11:43:76:F8:EF
          inet adr:192.168.0.2 Bcast:192.168.0.255 Masque:255.255.255.0
          adr inet6: fe80::211:43ff:fe76:f8ef/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Packets reçus:16553 erreurs:0 :0 overruns:0 frame:0
          TX packets:10968 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          Octets reçus:21587912 (20.5 MiB) Octets transmis:867690 (847.3 KiB)
          Interruption:201

eth1 Lien encap:Ethernet HWaddr 00:12:F0:41:E2:98
          inet adr:192.168.0.31 Bcast:192.168.0.255 Masque:255.255.255.0
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          Packets reçus:0 erreurs:0 :0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          Octets reçus:0 (0.0 b) Octets transmis:0 (0.0 b)
          Interruption:177 Adresse de base:0xe000 Mémoire:dfdfd000-dfdfdfff