If you lost your Windows Administrator password (XP) dont panic here are some method that will help without reinstalling it.
Or you could, if you have a FAT32 file system, just boot to a Win98 bootdisk and rename the SAM file (registry Hive) in the C:\WINNT\system32\config folder to something else. Of course this will remove all accounts on the system and you will need to rebuild them. If you are using NTFS then boot to the Win2000 CD and do this from the Recovery console.
this method i get it from internet long time ago and i used this technique and based on my experience it's working.
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