Have you been trying to install Microsoft Windows Vista Service Pack 1 and ended up with a 'Configuring Updates' message and some reboots? The following solution worked fine for me:
Find a way to a command prompt or file manager which handles NTFS partitions. Examples are: starting another OS from a dual-boot system, use the Vista DVD and boot it up or use a bootable Linux CD/DVD. Once reached a working operating system you only have to delete the pending.xml file from the \Windows\winsxs\ folder.
Using the command prompt of the Vista DVD, (Boot the DVD and click on 'Repair your computer' and select the correct operating system. Then press 'Next' and open the 'Command Prompt') you have to enter the following commands:
Make sure you are working on the right drive/partition! You can check the disk label by entering 'dir' and read the first line of the output given by the command.
The file will be removed. Then reboot the system and let it continue the third stage - but this time correctly.
A while ago I had a laptop with similar problems. It didn't loop but started updating everytime Windows started. I fixed this by disabling automatic updates and then update manually. Install every update for Windows and after downloading reboot Windows. Then turn automatic updating back on and it might be working correctly again.