i945G And Vista SP1 Don't Play Well Together
“The service pack also won't work with computers that use certain, widely-deployed audio drivers from Realtek and certain drivers for security devices manufactured by Symantec. Microsoft has published a full list of drivers that are incompatible with the service pack.”
This issue could cause trouble for an untold number of users because the 945-family of chipsets and Realkek audio chips are extremely common, especially in lower-end machines. The Redmond giant is urging users to make sure that their drivers are up to date before performing an upgrade as a possible remedy.