Additional SQL Server features and topics not covered by specific categories
I played with this and also read the link that Amelia provided. The UI is misleading, because that it is not the place it is looking. It's looking in your %TEMP% folder. Open a command-line window and type
echo %TEMP&
to find out.
Once I had place the cab file there, Next lit up.
Also, I think you have the wrong file. SPO_4.5.12.120_1033.cab appears to be the right guy.