Check to ensure that your computer has available hard drive space for the installations. Both editions of Cubase require large amounts of physical memory. In addition, double-check to ensure that your computer meets the minimum system requirements needed to operate both packages.
Insert the Cubase 5 disc into your computer and follow the on-screen instructions to install the software. Take note of the location you specify for the install to take place. You will need to specify a different location for your Cubase SX3 installation.
Insert the Cubase 3 disc into your computer and follow the on-screen instructions. When you are prompted to specify an install location, either choose or create a new folder separate from your Cubase 5 installation. If you install the programs in the same location, the previously installed version will be erased.
Launch each program to ensure the installations were performed correctly. If you experience problems with either program, reinstall the malfunctioning software. If your problems persist, contact a representative at Steinberg.