Please download the setup again from Internet and keep a copy of it for future use.
Please download both files, Navigate to the directory where you saved the installation files and double-click the .exe(file1), this would extract the Ps CS5 installation files.
After the files finish extracting, the installer launches automatically. If it doesn’t, go to the folder that contains the extracted files. Double-click Set-up.exe to begin installation.
Follow the instructions mentioned carefully.