You can try this options:
- Clean up temporary files and registry key issues with a free tool like CCleaner, and try to reinstall SP1 update.
- Download off-line version of Windows 7 Service Pack 1 and try to install it.
- Try to update microsoft update, and try again the update.
Notes:
It is recommended you verify your version of windows going to Computer > right-click properties.
Also you can check it out if you go to Start > type "cmd" in the search box > type "winver" in cmd. On the version, you will also see if you have the service pack 1 or no.
Please let me know if you still need help or if you solved the problem.