My friend's lappy (which also runs XP Home) does not have this option.
Are you sure you are looking at the wireless adapter and not the ethernet one?
I'll assume that you have checked for the switch and turned it on.

Go into the Device Manager and expand the Network Adapters. You should see at least 2 entries, one for the ethernet and one for the wireless. Open the properties of the wireless one and see if it is reporting it is enabled and working.

If there is no wireless adapter shown in the Device Manager then, a) It does not have a wireless adapter fitted or b) the adapter has been disabled in the BIOS. If it is the former there is not much you can do except use a plug in type. If it is the latter, then you will have to go into the BIOS and enable it.