Invalid XP serial number

1. go to "run" > type "regedit"

2. find this, "HKEY_LOCAL_MACHINE\SOFTWARE|Microsoft\Windows NT\CurrentVersion\WPAVEvents

3. double click "OOBETimer", > delete one "
value data"

for example,

CA 82 B8 55 D4 04 B5 CF E
CC 5B 24 97

change to >

82 B8 55 D4 04 B5 CF E
CC 5B 24 97

4.go to "run", > type "%systemroot%\system32\oobe\msoobe.exe /a

5.click the "Yes, i want to telephone a customer service.....", >then click "next"

6.click "change the product key"

7. after that , click "remind me later", and restart the WinXP

8. after restarting, go to "run", > type "%systemroot%\system32\oobe\msoobe.exe /a"
you can see Windows is already activated.Click Ok to exit.

then you can update your winXP to SP1