|"I downloaded Windows-XP on my Toshiba laptop"|
The word is INSTALLED, not downloaded.
What you have failed to do however is install drivers for the inbuilt wireless network card, if they exist at all. Did the laptop come originally with XP? Do you have a driver disk for it? Have you visited toshiba to see if they have drivers available for download?
Have you looked in devicemanager to see if any other devices are lacking drivers?
Goin' Fishin' (Some day)