If you want to register Windows XP quickly, without any program, here is what to do.
Open the text editor and copy and paste the text below. After paste it, save the file as xpreg.reg (or any name.reg) and double click it. Click yes to add the data to registry.
HKEY_LOCAL_MACHINESYSTEMWPA]
[HKEY_LOCAL_MACHINESYSTEMWPAKey-G4XTBRDJMGP7G4WJTJK48]
"ProductID"="55274-649-2198483-23859"
"DigitalProductID"=hex:a4,00,00,00,03,00,00,00,35,35,32,37,34,2d,36,34,39,2d,
32,31,39,38,34,38,33,2d,32,33,38,35,39,00,2e,00,00,00,41,32,32,2d,30,30,30,
30,31,00,00,00,00,00,00,00,11,9e,64,4d,f2,2a,79,4a,9c,ab,11,1b,58,3d,05,00,
00,00,00,00,fa,c9,43,3f,01,d9,0f,00,01,00,00,00,00,00,00,00,00,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,37,35,37,32,33,00,00,00,00,00,00,00,b4,0d,
00,00,e9,13,68,27,78,01,00,00,86,01,00,00,00,00,00,00,00,00,00,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,f8,e3,6a,02,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,
00,00,00,00,00,00,00,00,00,00,00,00,00
[HKEY_LOCAL_MACHINESYSTEMWPAMediaCenter]
"Installed"=dword:00000000
[HKEY_LOCAL_MACHINESYSTEMWPAPnP]
"seed"=dword:40a5a15f
[HKEY_LOCAL_MACHINESYSTEMWPASigningHash-XKDVQR6363B4W3]
"SigningHashData"=hex:e8,76,64,dd,2e,f5,16,73,aa,aa,51,7e,0f,22,77,e0,7b,74,a6,
72,f6,18,ce,d8,d7,16,17,6f,24,9b,18,8c,b3,7c,4a,cc,cc,0b,43,4b,8d,b1,e2,48,
56,38,e8,36,9e,0c,38,98,06,ba,6a,2b
[HKEY_LOCAL_MACHINESYSTEMWPATabletPC]
"Installed"=dword:00000000