Loss of WLAN following crash Compaq Pressario A900?

My laptop crashed and I was unable to re-boot. A friend of my son said they could help but when they returned the laptop they were unable to get Windows Vista to run and loaded XP Pro. All my data was still on there but I have been unable to get WLAN enabled. HP Wireless Assistant is saying that the device has been disabled by the Windows Device Manager but when I go to that there is no listing for WLAN devices. How can I enable/re-install the WLAN device for wireless connectivity? I have re-installed the driver from the HP driver download site but it hasn't changed the situation.