You can run Sony software and calibre on the same computer. Justbe sure you don't run both programs at the same time.
Download and install calibre, the Sony software and adobe editions. You will need to setup a free adobe digital editions account on your laptop and authorize your reader on that account. Just google adobe digital editions to do this. With a valid ADEaccount you can purchase from the Sony bookstore, kobo and books onboard as well as others. Just make sure you buy drmfree files or Adobe PDFs and pubs.
Calibre can manage any books you buy or download, but it cannot convert drm files.
You can also download free ebooks directly to your Sony here in the ebooks section, at
www.feed books.com, and at many books.net There are many other resources for free ebooks.