ur have to buy a new win xp .cd now and install that . or call microsoft tell them what happen and you can buy a license fromthem but watch oput microsoft will ask a lot of $$$$ ur be better off buying windows xp from walmart you can buy it for $
Microsoft Windows XP Home Edition With Service Pack 2
Online only!
$191.92
Microsoft Windows XP Home Edition OEM Version
Online only!
$119.98
from walmart microsoft will ask more then that
http://www.walmart.com/search/search-ng.do?search_constraint=0&search_query=windows+xp&Continue.x=24&Continue.y=17&Continue=Find&ic=24_0
when the 30 days activate is up you cant login to ur desktop windows xp will shut down
call microsoft and buy a electronic license of Windows XP Home for $99
"Qualifying customers who fill out a counterfeit report, provide proof of purchase, and send in their counterfeit CDs may receive a genuine copy at no cost. Customers may also purchase an electronic license of Windows XP Home for $99 or Windows XP Pro for $149, or from their favorite local resellers,"