Follow the given steps to install Windows 7 Service Pack 1
In Windows, search the registry in the search box given below, on opening it, it will ask for permission to make changes in your device, make it yes.
After opening the registry, follow this path HKey Local Machine>System>Current Control Set>Control>Windows>CSD Version.
Right-click on CSD Version and save by typing 100 in value.
After that restart your computer or laptop. While restarting it will take some permissions set it to yes
This may take 10 to 20 minutes. After this Windows 7 Service Pack, 1 will be installed on your computer or laptop.