You can do lot by changing the Windows Registry. This is another hack that allows to install crucial security updates to Windows XP SP2 after Microsoft discontinued support. F-Secure has come up with a registry hack base on the hack provided for the Grand Theft Auto IV. Simply the hack allows you to install the game on SP2 even though it requires SP3. They used the same changes to install the security updates and confirm that it is working perfectly.
"It turns out that an SP2 system will think its SP3 if you edit this key: HKLM\System\CurrentControlSet\Control\Windows, and edit the DWORD value CSDVersion from 200 to 300 (and reboot)."
however, it is always recommend to update to the latest Service Pack.