Problem solved with the last few updates to Driver Sweeper.DennisMenace said:Finally managed to get Windows 7 SP1 installed after various strange error messages - turns out Driver Sweeper had removed some system files (ATI drivers) which made Windows think it was corrupted, so would not update (other updates were fine, but not SP1). Unfortunately, the error messages gave no clue as to the corrupted/missing files, so it took a fair bit of googling to find the cause.
If anyone else has the same problem, check the Driver Sweeper website - the removed files can be downloaded and reinstalled, then SP1 should install fine.
http://phyxion.net/Driver-Sweeper/Driver-Sweeper/Version-3-0-0/
The above works fine, the version on Guru3D website is the problem it links to download version 2.1.0 which dates back to 2009.