who can't i find registration numb.w xp ?

[popeye09]

who can't i find registration numb. i now is stupit but i may be some body how cant help ilustrate me about remuve exchage registration number from my windows xp copy.. many times i did format my comp. and reintall windows again but i can't wet up dates from the web becuose it is a copy.. yes wondering if it is posible to change that numb. ore how to make this a legal copy.. that numb. is hide some were ?