7a903d07ba30418321690a is the folder that sp2 unpacs to when you run the file
spinstall.exe is the file that auto runs from that folder to install sp2 files to the correct locations within vista
if the file is missing or corrupt it means you have a bad download of sp2
or possibly you do not have access rights to run it
try running in safe mode or from an elevated command prompt. Elevated command prompt
Open the Start Menu. Click on All Programs and Accessories, then right click on Command Prompt and click on Run as administrator.