Thanks Corkyg for the reply.
The Laptop is Acer Aspire- 7220. Why I say that it died slowly that once it didn't show at the time of start up. As one windows (vista) update had happened just before that, I thought may be it is a driver problem. I restored to before update instal situation and restarted my laptop. At that it worked normally. Next day I again saw one windows update leading to restart of laptop (it is usually kept on) and found that wireless was not working. The diagnosis showed that it failed to locate a wireless device.
I thought may be this time also it is a driver problem caused by windows update and again restored to earlier date, but this time wireless did not work at all. I tried to install latest drivers (which I found were already installed) but it showed a message that the driver instal did not detect the wireless device.
I checked in the BIOS. There also it is not showing. Then I concluded that may be the hardware has died. I checked the card'sconnectors of antenna, and found them properly fixed ( I opened the bottom panels of the laptop to check the same)
Is my conclusion correct? Has my wireless card died or the motherborad is dying? Rest of the functions are OK.