Here is some info on SP1 from the latest Windows 7 newsletter:
Follow-up: Windows 7 SP 1
Last week, we took a look at Service Pack 1 for Windows 7, and as usual, results were very mixed. Some of our readers experienced flawless installations while others had a myriad of problems. Some were just unable to install the service pack, and a few reported "bricked" machines (these seem to be mostly Dells, especially those running 64 bit Windows, and a fix from the Dell Support forums was posted in our forum). A few readers reported that their desktop icons disappeared after the installation of the service pack. And some reported problems with applications (for example, Jon M. said Outlook keeps crashing after the SP1 installation).
I got email from several readers who said that they were unsuccessful at installing SP 1 until they wiped the disk and installed Windows 7 without the "crapware" programs that are installed by the computer manufacturers, and then SP1 installed with no problem.
The following advice came from Jim B.: "If you use Remote Server Administration Tools (RSAT) be sure to have them installed before installing SP1. RSAT for Windows 7 SP1 will not be available until April and there are many reports of people not being able to install the current RSAT on an SP1 machine."
If you're having problems getting SP1 to install, check out the forums on TechNet. Here is one thread that deals with Error C000009A:
http://www.win7news.net/IWRY1T/110317-Error-C000009A