I’ve heard a few stories if people applying SP1 to Vista or some other update to Vista and suddenly something stops working. For example, one user I heard about suddenly found that his system wouldn’t detect USB flash drives after applying SP1. What can you do if this happens?
You can try running System File Checker (SFC.exe) on the affected computer. SFC is a command-line tool used with Windows File Protection (WFP) that can scan protected operating system files and verify their versions. To use SFC, open an elevated command prompt and type sfc scannow at the command prompt. This scans your protected operating system files and replaces any incorrect versions found with the correct versions of the files. And if any files can’t be replaced by SFC, you can follow the instructions in this KB article to correct the situation.
