i purchased a dell inspiron 15R a few days back. it had ubuntu 12.04 preinstalled. the guys at the shop installed win8 on it 4 me. but later i decided to shift 2 ubuntu. & I'm kinda a new user. i installed it back using the recovery disk. now everything is working fine except the wi-fi. can any1 please help me out??
Trying to figure out what's going on with wireless can be quite tricky if all we have to go by is "the wireless isn't working". One of the biggest problems can be hardware compatibility issues. I would hope since your computer shipped with 12.04 lts, that the wireless card is supported in that version, but it is a 2 year old version of ubuntu at heart. I suggest you try a live usb drive of a newer version and see if the wireless works then, this will help eliminate hardware issues and with a new machine you will generally have more stuff work out of the box.
You can download ubuntu 14.04 here: http://www.ubuntu.com/download/desktop
Make a live usb stick in ubuntu: https://help.ubuntu.com/community/Installation/FromUSBStick
Make a live usb stick in windows: http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-windows
I have had the same problem if it is connect in the network panel, and if it is not connect in the network panel you have to delete the old one, and add a new hidden wifi. and you have to in the terminal type:
rfkill list lspci lsmod wlan0 lsusb -D wlan0
and then scan the port, and in the terminal type:
nmap -v -iR 10000 -Pn -p port
and this might work fine this way.