Hello
Install a program the installer usually needs to write to C:\Program Files, C:\Program Files (x86), and C:\Windows. All of those directories are protected by the Operating System and can only be written to by an administrator.
Your other option is to push the software through Group Policy. That would allow to you to install the software on computers in the OU without users having administrative access. To do you will need MSI installation packages for each program you want to install.