Maybe you’ve had a bad experience with a service pack in the past. Maybe you just don’t like change. Whatever the reason, if you’re stubbornly clinging to SP2, but you need to apply a critical security update that requires SP3, there is a registry edit you can do that will make XP SP2 appear to be an SP3 machine.
Microsoft doesn’t support it, and you do it at your own risk, but here are the steps:
1. Open your registry editor and navigate to: HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Windows
2. In the right pane, double click the value CSDVersion.
3. In the value data field, change the hexidecimal value (200) to 300.
4. Click OK.
5. Close the registry editor and reboot.