Hi,
Have you checked in Device Manager (go to Start > Control panel > Device manager) that the WLAN network adapter (listed under Network Adapters) is working correctly?
If there is a red cross listed next to the WLAN entry, right click on the entry and select 'enable' then see if your wireless works.
If there is a yellow explanation mark next to the entry, right click on the entry and select ''Properties'' check the staus of the device and see if updating the drivers restores the function.
If there is no WLAN (or wireless ) entry at all restart your PC and go into the BIOS area and see if there is a WLAN enable/disable option listed there.
Here is a link to the drivers for your PC. Ensure that you select Windows XP as your OS. Scroll down to Driver - Network , click on the + sign then locate the '''wireless''' driver download applicable to which type of wireless device that you have as listed in Device manger. It will either be HP Wireless or Belkin wireless. Click on the download button to download the driver to your PC so that you can install it.
http://h20565.www2.hp.com/hpsc/swd/public/readIndex?sp4ts.oid=3459248&swLangOid=8&swEnvOid=1093