Problem opening xlf document on newly downloaded trados

Please can you help me. I am having big problems with the importing of an xlf document.
I downloaded a trial version of trados onto a work laptop and could save and open xlf documents without any problems. The trial then ran out and I purchased the starter software. As the starter software could not be used on a work laptop, I then purchased a laptop that I could download the software onto. The xlf document is not recognised on the machine and I cannot open it. How can I convert the document to the relevant file. What do I need to do to be able to open it? Please help me. Thanks, Emma