is it definitely wireless?
click start > control panel and then system, click on the hardware tab and then select device manager, look for network adaptors and click the little plus next to it.
Does it say it has a wireless card?
also look at all the keys on the keyboard, has any of them got another coloured symbol on them that looks at all like this
http://h10025.www1.hp.com/ewfrf-JAVA/Doc/image s/c00192518.jpg
if so hold down the fn key and press that to enable/dissable wireless