Please open a terminal and do:
sudo apt-get install linux-headers-generic
sudo apt-get install --reinstall bcmwl-kernel-source
sudo modprobe wl source : http://askubuntu.com/questions/224052/hp-pavilion-tx2000-wifi-adapter-no-longer-works-after-moving-from-12-04-to-a-1
root@jati-laptop:~# iwconfig
lo no wireless extensions.
eth0 no wireless extensions.
wlan0 IEEE 802.11bg ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
pan0 no wireless extensions.
root@jati-laptop:~# ifconfig wlan0 down
root@jati-laptop:~# ifconfig wlan0 up
SIOCSIFFLAGS: No such file or directory
root@jati-laptop:~# iwspy
lo Interface doesn't support wireless statistic collection
eth0 Interface doesn't support wireless statistic collection
wlan0 Interface doesn't support wireless statistic collection
pan0 Interface doesn't support wireless statistic collection
root@jati-laptop:~# iwconfig
lo no wireless extensions.
eth0 no wireless extensions.
wlan0 IEEE 802.11bg ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
pan0 no wireless extensions.
root@jati-laptop:~# lspci | grep 'wireless'
root@jati-laptop:~# lspci
00:00.0 RAM memory: nVidia Corporation C51 Host Bridge (rev a2)
00:00.1 RAM memory: nVidia Corporation C51 Memory Controller 0 (rev a2)
00:00.2 RAM memory: nVidia Corporation C51 Memory Controller 1 (rev a2)
00:00.3 RAM memory: nVidia Corporation C51 Memory Controller 5 (rev a2)
00:00.4 RAM memory: nVidia Corporation C51 Memory Controller 4 (rev a2)
00:00.5 RAM memory: nVidia Corporation C51 Host Bridge (rev a2)
00:00.6 RAM memory: nVidia Corporation C51 Memory Controller 3 (rev a2)
00:00.7 RAM memory: nVidia Corporation C51 Memory Controller 2 (rev a2)
00:02.0 PCI bridge: nVidia Corporation C51 PCI Express Bridge (rev a1)
00:03.0 PCI bridge: nVidia Corporation C51 PCI Express Bridge (rev a1)
00:05.0 VGA compatible controller: nVidia Corporation C51 [Geforce Go 6150] (rev a2)
00:09.0 RAM memory: nVidia Corporation MCP51 Host Bridge (rev a2)
00:0a.0 ISA bridge: nVidia Corporation MCP51 LPC Bridge (rev a3)
00:0a.1 SMBus: nVidia Corporation MCP51 SMBus (rev a3)
00:0a.3 Co-processor: nVidia Corporation MCP51 PMU (rev a3)
00:0b.0 USB Controller: nVidia Corporation MCP51 USB Controller (rev a3)
00:0b.1 USB Controller: nVidia Corporation MCP51 USB Controller (rev a3)
00:0d.0 IDE interface: nVidia Corporation MCP51 IDE (rev f1)
00:0e.0 IDE interface: nVidia Corporation MCP51 Serial ATA Controller (rev f1)
00:10.0 PCI bridge: nVidia Corporation MCP51 PCI Bridge (rev a2)
00:10.1 Audio device: nVidia Corporation MCP51 High Definition Audio (rev a2)
00:14.0 Bridge: nVidia Corporation MCP51 Ethernet Controller (rev a3)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
03:00.0 Network controller: Broadcom Corporation BCM4312 802.11a/b/g (rev 02)
root@jati-laptop:~# 