I have a dell inspiron 1504 laptopof dec 2006 make. Till now wireless was working. But since, 10 days wireless does not connect and I am forced to connect through cable and work.the os is windows xp sp3.

You need to check if you can 'talk' to your router and then confirm settings

Make sure the wireless option has not been turned off by mistake. It could either be a switch on the laptop or a Fn key setting.