Hi Liam,

Assuming that you are trying to install a compatible version of iTunes, you can try the methods below:

Method 1: Right click on the setup file and, from the drop down menu, select "run as administrator".

Method 2: Open command prompt in elevated mode and, then unregistered and re-register Windows Installer.

1. In the Start search box and then type 'cmd', when the command application appears at the top of the start window, right click on it and, from the drop down menu, select 'run as administrator' and type each of these commands in the command prompt and press Enter

• msiexec /unregister 
• msiexec /regserver

msiexec.exe belongs to the Windows Installer Component and is used to install new programs that use Windows Installer package files (MSI)

Method 3: Start the Windows Installer service

1. Click Start, type Services.msc and press {ENTER}
2. Double-click Windows Installer
3. Set the Startup type of Windows Installer to Manual
4. Click Start to start the service. Note down the error message if any.
5. Click OK.After that it should get installed successfully.

If the above mentioned steps don’t resolve the issue, you can try the below as well:

I hope this helps.

Regards,
Lokesh