go to Run prompt
GO to regedit
search for "HKEY_LOCAL_MACHINE"
then
go to "system"
then
go to "CurrentControlSet"
then go to "Control"
then go to "Windows"
search file "CSDVersion"
double click on it
change the value of "Value data"
for service pack 1 = 100
service pack 2 = 200
service pack 3 = 300
change the value and restart your machine
for help please check screen shots
Enjoy your service pack
