WLAN problem, can’t turn on wireless connecion card

I have Dell mini laptop model 1011 and have it plugged directly ito the router because I could not turn on the WLAN card to work wirelessly. Other computers on the LAN work fine wirelessly. I checked the Dell manual and it says to press Fn F2 to toggle this on and off for wireless or direct connection. But this toggle does not work. It shows it is NOT working wireless according to the icon in the desktop tray. I am running XP home with SP3. Runs OK as connected, but from time to time it disconnects me from the web and I then have to reboot to get back n the web. Can anyone assist? Sounds to me like the WLAN card is somehow defective. If so, can I relace it myself? I am not a pro – just a long time user Appreciate any assistance.