Windows 7 Service Pack 1 may fail to install properly on systems which have had the Driver Sweeper utility from Phyxion run against the Windows image. You could possibly encounter errors 0x800f0a13 or 0x800f0826 in your \Windows\Logs\CBS.log file that is similar to the following:
2011-02-23 10:47:55, Error CBS SPI: Driver directory C:\Windows\System32\DriverStore\FileRepository\atiilhag.inf_amd64_neutral_951c1812f542740a is missing
2011-02-23 10:47:55, Error CBS SPI: (CSPInstall::CompatibilityApplicabilityScan:1468)Inbox Driver check failed hr=0x800f0a13
Due to some recent forums feedback, before trying any of these workarounds please run the latest version of CheckSUR against your machine as it may resolve your issue. It is located here: http://support.microsoft.com/kb/947821
There are several workarounds for this issue:
Follow the steps from Phyxion on properly restoring the drivers: http://forum.phyxion.net/viewtopic.php?id=17
Mount your Windows installation media to a folder and manually copy the ATI files to the \Windows\winsxs directories (choosing to overwrite the files if they exist). The file names are:
Perform an inplace upgrade of Windows
UPDATE 2-28-11: There have also been issues seen when using the DriverCleanerDotNet tool as well.
Special thanks to Andre Ziegler for coming up with this information.