Did you recently apply Windows updates including an optional/recommended update called ""intel driver update for intel(r) centrino(r) advanced-n 6250 AGN"?
I applied this update on Thursday. The update failed to apply and I immediately lost all forms of connectivity. A few Toshiba laptop users have noted the problem here:
I was able to fix my system:
(1) In Device Manager, I uninstalled the broken driver and chose the option to delete the driver file.
(2) Using another computer, I downloaded an old wireless driver from my system manufacturer's support site. In my case, that was here:
(3) I transferred the files by usb drive and installed the old driver. (Listed on the Toshiba site as version 188.8.131.52.0_184.108.40.206, released in March 2011.) The setup wizard claimed that it was interrupted before it could finish and that my system had not been modified. However, the wireless immediately began working again.
When I tried the drivers from Intel's support pages, they DID NOT WORK for me. My system may have needed customized drivers from Toshiba.
thanks for your response, but no, my problem is, I was never able to detect my wifi network. I tried to uninstall driver (including driver software) several times and installing Intel and Lenovo drivers too. No success. Network cannot be even detected.