Pat,
.Net 3.5 is on your computer but in their infinite wisdom, Microsoft dotted not install it by default in some of their OEM installs. 4.5 is not an upgrade, it simply runs side by side with 3.5 and most software running today requires 3.5.
To install it, go to your Control Panel and select Programs and Features. In the left column, look for something like add/remove system features (or something like that - I'm on the road on my iPad) and at the top of the list will be .Net 3.5. Check that box in front of that entry and it will be installed and then lamination pro will install just fine.
Lloyd