Came across this blog on another site,http://msinfluential...ing-xp-sp3.aspx
That details one of the causes of the non-boot issue some are having regarding SP3,
If you have an HP computer with a part number that ends with a 'z' you have an AMD-based computer. Other manufacturers have also shipped AMD-based computers, but it is unclear whether they have built their images the same way HP did.
The problem is that HP, apparently along other OEMs, deploy the same image to Intel-based computers that they do to AMD-based computers. Because the image for both Intel and AMD is the same all have the intelppm.sys driver installed and running. That driver provides power management on Intel-based computers. On an AMD-based computer, amdk8.sys provides the same functionality. Microsoft points out in a Knowledge Base article that installing both drivers on the same computer is an unsupported configuration, putting the blame on the OEM that deploys the image. The article in question was written when the same problem occurred after installing Service Pack 2 for Windows XP.
There is also a list of before and after fixes for anyone that falls into this category.