It's time to call HP. Some of their OEM versions required you use a HP supplied patch first. There is also some pirate version of XP out there, but I only bring it up since you are having an issue. HP doesn't use that version but I have run into it.
I am running a basic HP Pavillion 511W and SP2 would not download from Microsoft web site so I ordered the disc. Now it says it can not install because I am running a non Microsoft kernnel ???? What does this mean, and please I'm a newby so put it in laymans terms.