I have had problems installing service pack 1 on some SL510 machines running windows 7 after running a restore from Lenovo recovery disks. The SP1 installation would hang right in the middle. There is a microsoft tool that must be run after the sp fails (automatically included in updates from Windows Update), but running the tool was no help. The SP1 install would fail again. My solution was to update the BIOS to the latest one and then update the intel chipset drivers. I think the chipset drivers were the ones that fixed the problem. The chipset drivers were not installed through System Update. The message was "package not downloaded", but I installed them directly from the Intel site right here: http://www.intel.com/p/en_US/support/detect
After the chipset drivers were updated, SP1 installed normally.
BTW, my machines were running the 64-bit version of windows 7, but the problem may also affect 32-bit systems.