I take it the android tab has built in wireless (I know this is not an XP question).
if the wireless is built in - and not functioning correctly, it is most likely that either you have to turn on the wireless (button somewhere on the tab - or possibly software that you need to tell the tab to enable wireless - check the manafacturers website for the user manual).
the device driver was not installed correctly - you might need to reset the device back to factory - again you would need to get to the manafacturers website to find out how to do that for your specific model
if it still is not working - that would indicate a hadware fault. You can either get this fixed professionally - if under 1 year old the hardware may still be under warranty and you could get it repalced or fixed for free.